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Soft Tissue

Superpage 1

Revised: 12 November 2014
Copyright: (c) 2001-2014, PathologyOutlines.com, Inc.

Introduction

Soft tissue - normal


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 6 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Nonepithelial extraskeletal tissue, excluding supportive tissue of organs and lymphoid/hematopoietic tissue
● Includes fibrous tissue, adipose tissue, skeletal muscle, smooth muscle, blood vessels, lymphatics and peripheral nervous system
● Usually mesodermal in origin; peripheral nerves derive from neuroectoderm



Introduction

Sarcomas-general


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 6 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● 9,500 new cases per year in US
● Classified based on type of cellular differentiation, although most arise from multipotent mesenchymal cells that then differentiate along various cell lines
● Diagnostic errors are often due to lack of familiarity with rare lesions, not failure to perform immunostains (Am J Clin Pathol 2001;116:473)

WHO classification:
● Last revised in 2002 (Histopathology 2006;48:3), Table of Contents of WHO book-2002, World Health Organization classification with comments (Atlas of Genetics and Cytogenetics)

Clinical features
=========================================================================

● Usually arise de novo, not from benign tumors (MPNST may be an exception)
● Do not appear to arise from trauma
● May be caused by radiation therapy (MFH, extraskeletal osteosarcoma), foreign bodies (MFH, angiosarcoma) or chemical carcinogens (angiosarcoma)
● Recommended to diagnose with FNA, core biopsy or incisional biopsy so appropriate treatment can be determined in advance
● Congenital soft tissue tumors, even with high grade features, rarely have malignant behavior
● Nodal involvement uncommon
● Local recurrences show increased number of genetic changes, including loss at 9p, gains at 5p and 20q (Mod Pathol 2001;14:978)

Poor prognostic factors:
● Large size, deep seated versus superficial, retroperitoneum versus extremities, high grade, high stage, positive margins (associated with local recurrence)

Treatment
=========================================================================

● Ideally wide local excision with 1-2 cm margin of normal tissue
● If not possible due to anatomic constraints (neurovascular bundle, bone), a marginal excision (through pseudocapsule) or focally positive margin is acceptable
● Surgery should also remove site of prior incision
● Pre- or postoperative radiotherapy are routinely used for large, high-grade tumors or disseminated disease
● Amputation is reserved for unresectable tumors
● Surgical resection of pulmonary metastases often has value

Fine needle aspiration
=========================================================================

● Most specimens are recognized as sarcoma, and subtyping is most accurate in bone sarcomas and pediatric sarcomas
● Subtyping is often not possible in adult specimens, but this usually does not affect initial therapy (Am J Clin Pathol 2001;115:59)
● For staging information, click here



Introduction

Approach to diagnosis


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 6 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Modified from Sternberg
1) Is lesion reactive or neoplastic?
2) Is lesion malignant? (necrosis favors malignancy)
3) Is malignant lesion a sarcoma? (may be melanoma, carcinoma, lymphoma)
4) What type of differentiation is present? - assign to phenotypic category or classify as round cell, spindle cell, epithelioid, other
5) If sarcoma, what is the grade?



Introduction

Architectural patterns


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 17 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

Alveolar: alveolar rhabdomyosarcoma, alveolar soft parts sarcoma
Fascicular: fibromatosis, fibrosarcoma, neural tumors (benign or malignant), smooth muscle tumors, synovial sarcoma
Glandular: adenocarcinoma, biphasic synovial sarcoma, glandular MPNST
Lobular: clear cell sarcoma, epithelioid sarcoma, extraskeletal myxoid chondrosarcoma
Palisading: palisading intranodal myofibroblastoma, Schwann cells (neural tumors), smooth muscle tumors, spindle cell lipoma, synovial sarcoma
Pericytic vascular: mesenchymal chondrosarcoma, MFH, myopericytoma, solitary fibrous tumor/hemangiopericytoma, synovial sarcoma
Plexiform: nerve sheath tumors (neurofibroma, schwannoma), plexiform fibrous histiocytoma
Plexiform vascular: low grade fibromyxoid sarcoma, myxofibrosarcoma, myxoid liposarcoma, nodular fasciitis
Storiform: dermatofibrosarcoma protuberans (DFSP), fibrohistiocytic tumors, dedifferentiated liposarcoma, low grade fibromyxoid sarcoma, MFH, perineurioma



Introduction

Cell types


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 17 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

Epithelioid:
● Alveolar soft parts sarcoma, carcinoma (extension into soft tissue or metastases), clear cell sarcoma, epithelioid histiocytoma, epithelioid sarcoma, epithelioid variant of leiomyosarcoma, MFH or MPNST
● Extracellular myxoid chondrosarcoma, myxofibrosarcoma, rhabdoid tumor, schwannoma, synovial sarcoma or vascular tumors

Pleomorphic:
● Variants of leiomyosarcoma, liposarcoma, MFH, MPNST, myxofibrosarcoma, PHAT, pleomorphic lipoma or rhabdomyosarcoma
● Also melanoma and metastatic carcinoma

Round cell:
● Desmoplastic small round cell sarcoma, Ewings/PNET, mesenchymal chondrosarcoma, MPNST, rhabdomyosarcoma, round cell liposarcoma, schwannoma with neuroblastoma-like features, synovial sarcoma
● Also carcinoma, lymphoma, melanoma, neuroblastoma, poorly differentiated tumors

Spindle cell:
● Angiosarcoma, benign fibrous histiocytoma, benign nerve sheath tumor, DFSP, fibroma of tendon sheath (cellular), fibromatosis, fibrosarcoma, Kaposi’s sarcoma, leiomyoma, leiomyosarcoma, MPNST, nodular fasciitis, spindle cell lipoma, spindle cell variant of embryonal rhabdomyosarcoma, solitary fibrous tumor, superficial acral fibromyxoma, synovial sarcoma



Introduction

Grading


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 19 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Indicate in pathology report which grading system is used
● Grade is most important prognostic factor and indicator of metastatic risk in adults (Arch Pathol Lab Med 2006;130:1448)

Two grade systems - low grade and high grade:
Low grade: usually has limited ability to metastasize
High grade: cellular with mitotic figures and necrosis, but must evaluate in context of tumor type, age and location
● For example: superficial high grade MFH is unlikely to metastasize, but deep low grade MPNST is likely to metastasize
● Necrosis usually signifies high grade unless tumor is well differentiated and lacks pleomorphism


Grading systems - French Federation of Cancer Centers Sarcoma Group

General
=========================================================================

Grade 1: total score of 2-3 points
Grade 2: total score of 4-5 points
Grade 3: total score of 6-8 points

Tumor differentiation:
1 point: resembles normal adult mesenchymal tissue, may be confused with a benign lesion, such as well differentiated liposarcoma
2 points: histologic typing is certain, such as myxoid liposarcoma
3 points: synovial sarcoma, osteosarcoma, Ewing’s sarcoma/PNET, sarcomas of doubtful tumor type, embryonal and undifferentiated sarcomas

Mitotic count (count 10 successive high power fields [area of 0.17 mm squared] in most mitotically active areas):
1 point: 0-9 mitoses
2 points: 10-19 mitoses
3 points: 20 or more mitoses

Tumor necrosis:
0 points: no necrosis on any slides
1 point: less than 50% necrosis for all examined tumor surface
2 points: tumor necrosis of 50% or more of examined tumor surface


Grading systems - French Federation of Cancer Centers Sarcoma Group - grades of common sarcoma types

General
=========================================================================

● Angiosarcoma-poorly differentiated/epithelioid - 3
● Angiosarcoma-well differentiated/conventional - 2
● Chondrosarcoma-mesenchymal - 3
● Clear cell sarcoma - 3
● Epithelioid sarcoma - 3
● Fibrosarcoma-conventional - 2
● Fibrosarcoma-well differentiated - 1
● Fibrosarcoma-poorly differentiated - 3
● Leiomyosarcoma-conventional - 2
● Leiomyosarcoma-epithelioid / poorly differentiated / pleomorphic - 3
● Leiomyosarcoma-well differentiated - 1
● Liposarcoma-myxoid - 2
● Liposarcoma-pleomorphic - 3
● Liposarcoma-round cell - 3
● Liposarcoma-well differentiated - 1
● Malignant triton tumor - 3
● MFH-giant cell - 3
● MFH-pleomorphic with storiform pattern - 2
● MFH-pleomorphic without storiform pattern - 3
● Myxofibrosarcoma - 2
● Osteosarcoma - 3
● PNET - 3
● Rhabdomyosarcoma-alveolar / embryonal / pleomorphic - 3
● Synovial sarcoma – 3

Additional references
=========================================================================

Pathol Int 2007;57:121


Grading systems of soft tissue tumors - National Cancer Institute (US) tumor grading system

General
=========================================================================

Grade 1:
● Well differentiated liposarcoma
● Myxoid liposarcoma (grade 2 in French system above)
● Subcutaneous myxoid MFH
● Well differentiated malignant hemangiopericytoma with < 1 MF/10 HPF, no necrosis and no hemorrhagic areas
● Well differentiated fibrosarcoma with orderly herringbone pattern or well differentiated leiomyosarcoma with orderly fascicular pattern plus well differentiated cytologic features, no pleomorphism, no necrosis, < 6 MF/10 HPF
● Malignant schwannoma (MPNST) if resembles neurofibroma plus mitotic figures plus areas of high cellularity but < 6 MF/10 HPF
● Myxoid chondrosarcoma that is uniformly myxoid and hypocellular with no mitotic activity

Grade 2:
● Other histologic types with <15% necrosis

Grade 3:
● Extraskeletal Ewing’s sarcoma, PNET, extraskeletal osteosarcoma, mesenchymal chondrosarcoma, malignant triton tumor, or other histologic types with 15% or more necrosis

Additional references
=========================================================================

J Clin Oncol 1997;15:350, J Surg Oncol 1989;41:263



Introduction

Molecular / cytogenetics


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 17 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● RT-PCR or FISH of paraffin-embedded tissue for tumor fusion transcripts is useful (Am J Surg Pathol 2002;26:965, Am J Surg Pathol 2008;32:8)
Note: in table below, gene for first chromosome in translocation is listed first

Alveolar soft parts sarcoma: t(X;17)(p11.2;q25) - ASPL-TFE3 fusion gene
Aneurysmal bone cyst, extracellular: t(17;17)(p13;q12)
Angiomatoid fibrous histiocytoma: t(12;16)(q13;p11) - ATF1-FUS fusion gene or t(12;22)(q13;q12) - ATF1-EWSR1 fusion gene (also present in clear cell sarcoma)
Chondroid lipoma of soft tissue: t(11,16)(q13;p12-13); also in hibernoma
Chondrosarcoma, myxoid, extraskeletal:
      t(9;15)(q22;q21) - CHN-TCF12 fusion gene
      t(9;17)(q22;q11) - CHN-RBP56 fusion gene
      t(9;22)(q22;q12) - CHN-EWS fusion gene
Clear cell sarcoma: t(12;22)(q13;q12) - ATF1-EWSR1 fusion gene
Congenital fibrosarcoma / mesoblastic nephroma: t(12;15)(p13;q25) - ETV6-NTRK3 fusion gene
Dermatofibrosarcoma protuberans / giant cell fibroblastoma: t(17;22)(q22;q13) - COL1A1-PDGFB fusion gene
Desmoplastic fibroblastoma: occasionally t(2;11)(q31;q12) or 11q12 abnormalities
Desmoplastic small round cell tumor: t(11;22)(p13;q12) - WT1-EWS or t(21;22)(q22;q12) - ERG-EWS fusion genes
Ewing’s sarcoma/PNET, extraosseous:
      t(11;22)(q24;q12) - FLI1-EWS fusion gene
      t(2;22)(q33;q12) - FEV-EWS fusion gene
      t(7,22);(p22;q12) - ETV1-EWS fusion gene
      t(17;22)(q12;q12) - E1AF-EWS fusion gene
      t(21;22)(q22;q12) - ERG-EWS fusion gene
Inflammatory myofibroblastic tumor: translocations at 2p23 involving ALK gene
Lipoma: t(12;14)(q13-15;q23-24) or related changes involving HMGA2/HMGIC at 12q13-15
Liposarcoma-myxoid/round cell variants: t(12;16)(q13;p11) - TLS-CHOP/FUS fusion gene or t(12;22)(q13;q12) - CHOP-EWS fusion gene
Liposarcoma, well differentiated: marker ring or giant chromosomes derived from 12q13-15; amplification of MDM2 and CDK4
Low grade fibromyxoid sarcoma: t(7;16)(q32-34;p11) - FUS-CREB3L2 or t(11;16)(p11;p11) - FUS-CREB3L1
Rhabdomyosarcoma, alveolar: t(2;13)(q35;q14) - PAX3-FKHR or t(1;13)(p36;q14) - PAX7-FKHR
Synovial sarcoma: t(X;18)(p11.23;q11) - SYT-SSX1 or t(X;18)(p11.21;q11) - SYT-SSX2 fusion genes
Tenosynovial giant cell tumor: t(1;2)(p11;q35-37)

Additional references
=========================================================================

Arch Pathol Lab Med 2006;130:1199, Adv Exp Med Biol 2006;587:99, Int J Clin Exp Pathol 2010;3:416
Arch Pathol Lab Med 2010;134:e1



Staging

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 9 March 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
=========================================================================
Primary tumor (T)
=========================================================================

TX: Primary tumor cannot be assessed
T0: No evidence of primary tumor
T1: Tumor 5 cm or less in greatest dimension
T1a: Superficial tumor
T1b: Deep tumor
T2: Tumor more than 5 cm
T2a: Superficial tumor
T2b: Deep tumor

Notes: Regional lymph nodes (N)
=========================================================================

NX: Regional lymph nodes cannot be assessed
N0: No regional lymph node metastasis
N1: Regional lymph node metastasis

Distant metastasis (M)
=========================================================================

M0: No distant metastasis
M1: Distant metastasis

Histologic grade (G)
=========================================================================

GX: Grade cannot be assessed
G1: Grade 1 of 3 (low grade)
G2: Grade 2 of 3
G3: Grade 3 of 3 (high grade)

Stage grouping
=========================================================================
IA: T1a-b N0 M0 G1, GX
IB: T2a-b N0 M0 G1, GX
IIA: T1a-b N0 M0 G2-3
IIB: T2a-b N0 M0 G2
III: T2a-b N0 M0 G3
Any T N1 M0 Any G
IV: Any T Any N M1 Any G



Introduction

Syndromes (molecular / genetic) associated with soft tissue tumors


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 17 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

Bannayan Zonana syndrome:
● Multiple lipomas and hemangiomas
OMIM #153480

Beckwith-Wiedemann syndrome:
● Congenital overgrowth syndrome associated with alveolar rhabdomyosarcoma (Pediatr Dev Pathol 2001;4:550)
OMIM #130650

Carney syndrome / complex:
● Autosomal dominant multiple neoplasia syndrome with myxomas and pigmented lesions of skin and mucosa, due to mutation in PRKAR1A gene (OMIM #160980) or 2p16 abnormalities (OMIM #605244)

Carney triad:
● Gastric GIST, pulmonary chondroma and extra-adrenal paraganglioma (Mayo Clinic Proceedings 1999;74:543, Mayo Clinic Proceedings;1999;74:638)
OMIM # 604287

Gardner syndrome:
● Fibromatosis, familial adenomatous polyposis and osteomas
OMIM #175100

Kasabach-Merritt syndrome:
● Microangiopathic hemolytic anemia associated with childhood hemangioma or kaposiform hemangioendothelioma
OMIM #141000

Klippel-Trenaunay-Weber syndrome:
● Hemangiomas with hypertrophy of associated bone and soft tissue
OMIM #149000

Launois-Bensaude syndrome:
● Painless symmetrical diffuse deposits of fat beneath the skin of the neck, upper trunk, arms and legs
● Also known as multiple symmetrical lipomatosis, cephalothoracic lipodystrophy and Madelung disease

Li Fraumeni syndrome:
● Various soft tissue sarcomas, osteosarcoma, breast cancer, brain tumors, leukemia and adrenocortical carcinoma
● Usually due to p53 mutation
OMIM #151623

Lipomatosis, multiple syndrome:
OMIM #151800

Maffucci syndrome:
● Hemangiomas, enchondroma, chondrosarcoma
OMIM #166000

Mazabraud's syndrome:
● Fibrous dysplasia and intramuscular myxoma (J Cancer Res Clin Oncol 1998;124:401)

McCune-Albright syndrome:
● Major features are polyostotic fibrous dysplasia, cafe-au-lait skin pigmentation and precocious puberty
● Myxomas are minor feature (see Mazabraud’s syndrome)
OMIM #174800

Multiple endocrine neoplasia 1:
● Multiple lipomas may be a minor feature
OMIM #131100

Neurofibromatosis type 1:
● Neurofibroma, MPNST
OMIM #162200

Neurofibromatosis type 2:
● Schwannoma, neurofibroma, meningioma, astrocytoma, rarely perineurioma (Am J Surg Pathol 2006;30:1624)
OMIM #101000

Osler-Weber-Rendu syndrome:
● Telangiectasias
OMIM #187300

Proteus syndrome:
● Various cutaneous and subcutaneous lesions, including vascular malformations, lipomas, hyperpigmentation and nevi (eMedicine)

Stewart-Treves syndrome:
● Cutaneous angiosarcoma that develops in long-standing chronic lymphedema (eMedicine)

Sturge-Weber syndrome:
● Port-wine spot of face
OMIM #185300

Turner syndrome:
● 45 X0, associated with cystic hygroma (eMedicine), rarely familial desmoids or GIST

Sarcomas associated with hereditary nonpolyposis colorectal cancer:
● Uterine sarcomas, liposarcoma, leiomyosarcoma, and carcinosarcoma (Fam Cancer 2009;8:209)



Infections, inflammation and hematomas

Infections - general


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 18 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Usually due to direct extension from infections of skin, bone or viscera, or due to trauma or surgery



Infections, inflammation and hematomas

Granulomatous infections


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 18 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Due to tuberculosis, fungi, atypical mycobacteria (Clin Infect Dis 1995;21:65, Int J Tuberc Lung Dis 2007;11:96, Int J Tuberc Lung Dis 2011;15:811)

Case reports
=========================================================================

● Brucella gluteal abscess (Intern Med 2008;47:171)



Infections, inflammation and hematomas

Hematoma of soft tissue


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 18 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● May clinically resemble a tumor if deep seated
● Important to exclude a sarcoma with intratumoral hemorrhage
● Pseudoaneurysm may occur after intravascular procedures
● Post-operative seromas may persist for years and be confused with recurrent tumor

Sites:
● Usually near tensor fascia lata (upper thigh muscle, see drawing below)

Case reports
=========================================================================

● In tensor fascia lata (Dermatol Online J 2001;7:6)
● Giant chronic expanding hematoma of thigh (Joint Bone Spine 2008;75:64)
● Mass of thorax (Yonsei Med J 2007;48:337)

Drawings
=========================================================================



Usually near tensor fascia lata (upper thigh muscle)

Treatment
=========================================================================

● Complete surgical excision, including pseudocapsule

Clinical images
=========================================================================



Lesion of lateral thigh


Perforating vessel (arrow) from tensor fascia lata appears to run into the mass


Lobulation with dense fibrous pseudocapsule and chocolate-brown fluid

Micro images
=========================================================================



Cystic cavity with necrotic debris, fibrin and blood costs


Cyst wall has hyalinized fibrous tissue, chronic inflammation and granulation tissue



Infections, inflammation and hematomas

Necrotizing fasciitis


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 18 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Uncommon fulminant soft tissue infection characterized by extensive fascial necrosis
● Usually due to group A streptococci, also community-acquired MRSA (Surg Infect (Larchmt) 2008;9:469)
● May be due to Clostridium perfringens and cause gas gangrene (Cases J 2008 Oct 20;1(1):252)

Clinical features
=========================================================================

● Fatal if untreated
● 15% mortality even if treated (Epidemiol Infect 2009;137:1609)
● Particularly serious in patients with badly controlled diabetes (Diabetes Res Clin Pract 2008;80:218)

Treatment
=========================================================================

● Promptly start antibiotics and aggressive debridement (World J Emerg Surg 2007;2:19, J Am Acad Orthop Surg 2009;17:174)

Case reports
=========================================================================

● Due to Pseudomonas (Intern Med 2008;47:553)

Clinical images
=========================================================================



Gas gangrene


Right shoulder


Left leg

Micro images
=========================================================================



Infected tissue with gas-inclusion between the muscle fibers


Gram positive rods

Gluteal gas gangrene with necrotizing fasciitis #1, #2

Gas gangrene #1, #2

Necrotic muscle with gas bubbles but minimal inflammation

Leg lesion

Necrotizing fasciitis and panniculitis (pneumococci) #1, #2

Pneumococcal sepsis #1, #2

Septic thrombus

Associated vasculitis

Gram stain #1, #2, #3

Additional references
=========================================================================

eMedicine #1, #2
J Trauma Acute Care Surg 2012;72:560



Infections, inflammation and hematomas

PVP granuloma


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 18 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

Definition: granuloma due to injection of drugs containing polyvinylpyrrolidone (PVP)
● Rare (Am J Surg Pathol 1984;8:393)

Micro description
=========================================================================

● Focal cellularity, focally myxoid with foamy histiocytes containing vacuoles and PVP

Positive stains
=========================================================================

Histiocytes: mucicarmine, colloidal iron, GMS, Congo Red, Sudan Black B

Differential diagnosis
=========================================================================

● Myxoid liposarcoma
● Signet ring carcinoma



Infections, inflammation and hematomas

Tumoral calcinosis


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 18 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

Definition: large painless calcified masses in periarticular soft tissues, including elbows, hips, only rarely knees
● Also called calcium hydroxyapatite deposition in soft tissue, metastatic calcification
● Usage is imprecise - also refers to hereditary condition associated with massive periarticular calcification and any massive collection of periarticular calcification (Radiographics 2006;26:871)

Clinical description
=========================================================================

● Associated with trauma, renal failure, hyperparathyroidism, metastatic carcinoma, myeloma, scleroderma, hypermetabolic states, sarcoidosis
● Associated with mutations in fibroblast growth factor-23 gene and other genes (J Bone Joint Surg Am 2009;91:1190, OMIM #212900)
● Rarely is familial (Am J Surg Pathol 1993;17:788)

Laboratory:
● Elevated serum calcium, phosphate and Vitamin D
● Local recurrence common

Radiology description
=========================================================================

● Lobulated calcifications, separate from associated bone

Gross description
=========================================================================

● Large, multinodular, chalky masses

Micro description
=========================================================================

● Lobules of calcific material surrounded by histiocytic giant cells often containing small psammomatous calcifications

Micro images
=========================================================================


   
Calcification with foreign body inflammation

Differential diagnosis
=========================================================================

● Dystrophic calcification: contains dead tissue that is not rapidly absorbed; associated with coagulation necrosis, caseous necrosis, fat necrosis

Additional references
=========================================================================

● Tumoral calcinosis like lesions (Am J Surg Pathol 2007;31:15)



Adipose tissue

Embryology and physiology of adipose tissue


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 30 October 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

Embryologic development of adipose tissue
=========================================================================

● Stage I: prior to 14 weeks of gestation, loose spindle cells and ground substance are present
● Stage II: aggregates of mesenchymal cells condense around proliferating primitive blood vessels
● Stage III: capillaries proliferate into rich network, preadipocytes become stellate and organize into lobules
● Stage IV: fine lipid vacuoles develop within cytoplasm
● Stage V: adipocytes accumulate within rich capillary network and perilobular mesenchyme condenses at periphery of lobule to form fibrovascular septa at week 24 (Early Hum Dev 1983;8:1)
● Brown fat has similar development, but contains large mitochondria with uncoupling protein 1 (OMIM 113730); white fat progenitor cells can also induce brown adipogenesis through mir 16a signaling pathway (PLoS Biol 2012;10:e1001314)
● Brown fat deposits are well established by month 5 of gestation, particularly in posterior cervical, axillary, suprailiac and perirenal regions
● Adipocyte development is closely associated with angiogenesis: (a) fat appears first in well vascularized regions; (b) adipocytes synthesize lipoprotein lipase (transports serum triglycerides into adipocytes), which is transferred to luminal surface of capillary endothelium; (c) vasculature functions as a progenitor niche and may provide signals for adipocyte development (Science 2008;322:583)

Pathophysiology
=========================================================================

● Fat development is controlled by CHOP gene, which mediates differentiation of fibroblasts into adipocytes and growth arrest of terminally differentiated adipocytes; translocation of CHOP in myxoid liposarcomas may remove normal inhibition on CHOP
● At birth, amount of adipose tissue increases for next 10 years with overall growth; at puberty, adipocytes increase in size and number
● Brown fat is widely distributed in children in interscapular region, around neck vessels and muscles, around mediastinal structures, near lung hila and around abdominal viscera
● Some adipocytes may originate from neural crest (Development 2007;134:2283)



Adipose tissue

Normal white fat


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 30 October 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

Terminology
=========================================================================

● Also called White Adipose Tissue (WAT)
● Cells are called adipocytes

Sites
=========================================================================

● Subcutaneous, mediastinum, abdomen, retroperitoneum

Pathophysiology
=========================================================================

● Main function is energy storage as lipid, which is mobilized to other tissues depending on metabolic needs
● Triglycerides circulate in blood as chylomicrons; the enzyme lipoprotein lipase, produced by adipocytes and present on luminal surface of endothelium, converts triglycerides to free fatty acids; free fatty acids are taken up by adipocytes and converted to triacylglycerol, which is stored within cytoplasmic lipid droplet of adipocytes
● Adipocytes also secrete leptin and IL6, but their effects in humans are not well defined
● Stromal cells also convert androstenedione to estrone, the main source of estrogen in men and postmenopausal women

Gross description
=========================================================================

● Homogeneous, yellow, greasy surface, faint fibrous septa

Micro description
=========================================================================

● Uniform large spherical cells up to 120 microns; lipid droplet pushes nucleus to periphery and deforms it to a thin crescent
● Cytoplasm usually has single, clearly delimited vacuole
● Cells are clear because cytoplasmic fat dissolves during tissue processing
● Nucleus may have central vacuole or Lochkern
● Very thin membranes are present between cells

Micro images
=========================================================================



White adipose tissue and vasculature


Adipocytes along arteriole in mesentery O stain


White adipose tissue


Fat emboli in lung-Oil Red O stain

Other images: mature adipose tissue #1; #2

Virtual slides
=========================================================================



Fat (adipose tissue)

Positive stains
=========================================================================

● Vimentin (nonspecific), S100 (primarily for mature adipocytes), calretinin (also stains lipoma and liposarcoma, Hum Pathol 2006;37:312)
● Oil red O and Sudan Black stain neutral fat (must use frozen tissue because tissue processing removes fat); Oil red O also stains most carcinomas
● Nile blue sulfate stains neutral fat pink-red, and stains fatty acids/phospholipids blue
● Basement membrane is highlighted by PAS and reticulin

Negative stains
=========================================================================

● CD31, keratin, desmin, muscle specific actin

Electron microscopy description
=========================================================================

Pre-adipocytes - spindle cells with abundant endoplasmic reticulum and small spherical mitochondria
Mature adipocyte - large lipid droplet flattens nucleus against cytoplasmic membrane, variable pinocytotic vesicles; capillaries are close to adipocyte basement membrane

Electron microscopy images
=========================================================================



Subcutaneous adipocytes



Adipose tissue

Normal brown fat


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 30 October 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

Terminology
=========================================================================

● Also called Brown Adipose Tissue (BAT)

Sites
=========================================================================

● More conspicuous in infants (5% of body weight) and children; replaced with white fat over time
● Persists in adults in interscapular region, neck, mediastinum, axilla, retroperitoneum (perirenal) (diagram)
● Substantial amounts of metabolically active brown fat are present in healthy adults (N Engl J Med 2009;360:1518)

Pathophysiology
=========================================================================

● Main function is heat production (nonshivering thermogenesis), mediated through a dense vascular system and sympathetic nerves (Physiol Rev 2004;84:277)
● Brown fat mitochondria express uncoupling protein (UCP1), which uncouples fatty oxidation from ATP generation, which causes energy to be dissipated as heat
● Cold exposure leads to sympathetic stimulation of brown fat via norepinephrine binding to beta adrenergic receptors, then oxidation of fatty acids and heat production
● Protein-tyrosine phosphatase 1B is a modulator of brown fat adipogenesis (PLoS One 2011;6:e16446)
● Moderate intermittent stress can stimulate brown adipose tissue growth and thermogenic activity

Clinical features
=========================================================================

● Increased presence is associated with alcohol abuse, malnourishment and cachexia (may maintain body temperature in those with diminished subcutaneous fat), cardiovascular disease (Arch Pathol Lab Med 1992;116:1152); also Duchenne’s muscular dystrophy (Arch Pathol Lab Med 1988;112:550)
● Brown fat thermogenesis is visible with a thermal (infrared) camera in infants over neck and interscapular area
● Also important in animals coming out of hibernation, allowing them to rewarm quickly

Diagrams
=========================================================================



Sites of brown fat

Gross description
=========================================================================

● Red-brown (less lipid) to tan (more lipid) due to vascularity and numerous mitochondria
● Has glandular and lobular appearance

Micro description
=========================================================================

● Lobules of adipocytes, capillaries, nerves and connective tissue
● Adipocytes are smaller (25-40 microns) than in white fat, are polygonal with acidophilic multivacuolated and granular cytoplasm and central spherical nucleus with fine indentations

Micro images
=========================================================================



Multivacuolated cytoplasm


CD31

Positive stains
=========================================================================

● CD31 (Arch Pathol Lab Med 2006;130:480)
● Also mitochondrial membrane uncoupling protein (J Histochem Cytochem 1993;41:759)

Electron microscopy description
=========================================================================

● Numerous mitochondria and smaller amounts of lipid droplets

Additional references
=========================================================================

Wikipedia, J Mol Cell Biol 2010;2:23



Adipose tissue

Lipoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Benign tumor composed of mature white adipocytes with uniform nuclei resembling normal white fat
● Most common mesenchymal and soft tissue tumor (100x more common than liposarcoma)

Epidemiology
=========================================================================

● Most common soft tissue tumor - 16% of all mesenchymal neoplasms
● Adults, age 40+
● No gender or ethnic preference
● Rare in children
● Associated with obesity
Multiple lipomas: 5%, more common in women, often familial, associated with neurofibromatosis, multiple endocrine neoplasia syndromes, Bannayan syndrome (macrocephaly, hemangiomas and lipomas, Wikipedia)

Sites
=========================================================================

● Usually trunk, back, shoulder, neck, proximal extremities
● Rare on hands, feet, face, lower leg, retroperitoneum
● Usually subcutaneous (liposarcomas are usually deep seated)
● Unusual sites include oral cavity, pancreas, breast, intestines

Clinical features
=========================================================================

● Relatively static growth after initial growth period
● Does not regress even with starvation
● Becomes hard after application of ice

Case reports
=========================================================================

● 38 year old man with breast swelling (Eur J Plast Surg 2012;35:407)
● 52 year old man with mass in buccal mucosa (Dent Res J (Isfahan) 2011;8:48)
● 68 year old man with giant chest wall mass for 30 years (Interact Cardiovasc Thorac Surg 2012;15:323)

Treatment and prognosis
=========================================================================

● Benign, but 1-4% recur
● Excision is adequate treatment

Clinical images
=========================================================================



Right breast mass

Gross description
=========================================================================

● Bright yellow homogeneous fat with fine fibrous capsule (superficial lesions only) and trabeculae
● May be very large (particularly if deep)
● Greasy cut surface

Gross images
=========================================================================



Fatty mass with surgery-related hemorrhage


Various images


Encapsulated cardiac mass

Other images: encapsulated mass

Micro description
=========================================================================

● Mature white adipose tissue without atypia
● 2-5x variation in cell size (more than normal white adipose tissue), with obvious large cells up to 300 microns
● Cytoplasmic vacuoles are relatively uniform
● May have intranuclear vacuoles, thickened fibrous septa in buttocks, foot or hand
● May contain areas of fat necrosis with histiocytes, infarct or calcification
● Rarely contains bone or cartilage
● No mitotic figures
Note: diagnosis of lipoma requires presence of a mass

Micro images
=========================================================================



Unencapsulated subcutaneous lipoma


Mass has normal adult fat cells


Endobronchial lipoma

Other images: scapula, thorax

Virtual slides
=========================================================================



Left: site unspecified; right: retroperitoneal

Cytology images
=========================================================================



Adipocytes

Positive stains
=========================================================================

● Vimentin, S100, CD34 (slender spindle cells)
● Leptin, PAS (highlights capillaries), reticulin (surrounds each adipocyte)

Electron microscopy description
=========================================================================

● Univacuolar mature adipocytes that compress peripheral nuclei (Cancer 1982;50:102), pinocytotic vessels, cells are surrounded by external lamina

Molecular/cytogenetics description
=========================================================================

● 55%-75% of solitary lipomas with cytogenetic abnormalities have rearrangements of HMGA2/HMGIC at 12q13-15, although no associated clinicopathologic features are associated with the resulting fusion transcripts (Anticancer Res 2008;28:535, J Biomed Biotechnol 2011;2011:524067)
● Marker ring or giant chromosomes are extremely rare
● Multiple lipomas usually have normal phenotype

Molecular/cytogenetics images
=========================================================================



Schematic of HMGA2 and LPP

Differential diagnosis
=========================================================================

Normal fat: not circumscribed or encapsulated, not a mass
Pneumatosis cystoides intestinalis in small bowel: not actually adipocytes
● Mesenchymal cells producing acid mucopolysaccharide - vacuoles contain fluid and are not clear, nuclei are not deformed

Additional references
=========================================================================

eMedicine #1, #2, Atlas of Genetics and Cytogenetics, Stanford University



Adipose tissue

Angiolipoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

See also Breast chapter

General
=========================================================================

● Subcutaneous nodule composed of mature adipocytes, thin walled vessels and fibrin thrombi

Terminology
=========================================================================

Infiltrating (intramuscular) angiolipoma is no longer acceptable terminology because it represents a different lesion (Stanford University)
● May be an intramuscular large vessel hemangioma in which muscle has been replaced by fat (J Pediatr Orthop 1986;6:172)

Epidemiology
=========================================================================

● Arises shortly before puberty or in young adults
● Rare in children or older adults
● 5% familial

Clinical features
=========================================================================

● Usually skin, 2/3 in forearm and chest wall, can occur on thighs, distal extremity
● Rarely in the head and neck region
● Painful, usually multiple subcutaneous nodules (other painful nodules are angioleiomyoma, eccrine spiradenoma, glomus tumor and traumatic neuroma)
● May actually be hemangioma containing fat, not a mixed tumors

Case reports
=========================================================================

● 9 year old girl with swelling in the upper lip (J Oral Maxillofac Pathol 2012;16:103)
● 25 year old man with multiple tumors but with minimal adipose (Am J Dermatopathol 1995;17:312)
● 47 year old man with foot tumor (World J Surg Oncol 2008;6:11)
● 69 year old man with spinal tumor (Neurol Med Chir (Tokyo) 2011;51:539)
● 71 year old woman with epidural tumor (J Clin Pathol 2005;58:882)

Treatment and prognosis
=========================================================================

● Excision
● Does not recur or metastasize

Clinical images
=========================================================================



Various images

Gross description
=========================================================================

● Encapsulated, small (< 2 cm), yellow-red nodule in subcutaneous tissue

Gross images
=========================================================================



Various images

Other images: lobulated fat with thin fibrous septae and brown spots representing thrombosed capillary vessels

Micro description
=========================================================================

● Mature adipose tissue, branching capillaries and thick walled vessels with pericytes, particularly at periphery
● Hyaline/fibrin thrombi are an important diagnostic sign
● Cellular tumors are usually encapsulated with septation and fibrin thrombi (Am J Surg Pathol 1990;14:75)
● Mast cells are present
● Fibrosis in older lesions

Micro images
=========================================================================



Mature adipose tissue and prominent vasculature




Prominent vascular thrombi


Various images


9 year old girl wit lesion on lip

Other images: mature adipose tissue and prominent vasculature, prominent vascular thrombi

Virtual slides
=========================================================================



Virtual slide

Electron microscopy description
=========================================================================

● May have reduced number of Weibel-Palade bodies in endothelial cells (Hum Pathol 1981;12:739)

Molecular/cytogenetics description
=========================================================================

● Almost always normal karyotype

Differential diagnosis
=========================================================================

Kaposi’s sarcoma and angiosarcoma: - not circumscribed, usually not subcutaneous, atypia present, no scattered adipocytes



Adipose tissue

Chondroid lipoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Benign tumor of mature adipocytes, lipoblasts and myxochondroid stroma
● Rare, slow growing, painless
● First described in 1993 (Am J Surg Pathol 1993;17:1103)

Epidemiology
=========================================================================

● 80% female
● Median age 36 years, range 14 to 70 years

Sites
=========================================================================

● Proximal extremities and limb girdles, rarely oral cavity
● Intramuscular or subcutaneous

Case reports
=========================================================================

● 7 year old boy with thigh mass (Indian J Pathol Microbiol 2008;51:541)
● 33 year old man with hand mass (Case of the Week #52)
● 38 year female with painless thigh mass (Indian J Pathol Microbiol 2009;52:284)
● 55 year old man with pelvic mass (Korean J Radiol 2008;9:563)
● 71 year old woman with trunk mass (Skeletal Radiol 2004;33:666)
● Incidental finding at hip replacement surgery (J Surg Orthop Adv 2004;13:42)

Treatment and prognosis
=========================================================================

● Excision is curative
● Does not recur, metastasize or transform

Gross description
=========================================================================

● Median 4 cm, up to 11 cm, encapsulated, yellow or white

Gross images
=========================================================================



Well circumscribed mass


Lipomatous (arrows) and chondroid (*) areas


Thigh mass

Other images: yellow tumor

Micro description
=========================================================================

● Well circumscribed, nests and cords of small to medium, multivacuolated cells resembling lipoblasts, chondroblasts or hibernoma cells within a prominent chondromyxoid matrix with variable mature fat, rarely metaplastic bone (Skeletal Radiol 2008;37:475)
● Complex nuclear outlines
● Usually prominent vasculature with variable wall thickness
● May have hemorrhage and fibrosis, eosinophilic fibrinous matrix
● No pleomorphism, no atypia, no/rare mitotic activity, no mature hyaline cartilage

Micro images
=========================================================================



Well circumscribed tumor


Clusters of small to medium cells with vacuolated cytoplasm


Mature fat cells are present


Mature fat cells (*), lipoblast-like cells (arrowheads) and chondroid tissue (C)




Case #52


Various images

Virtual slides
=========================================================================



Virtual slide (USCAP)

Cytology description
=========================================================================

● Mature lipocytes and lipoblast-like cells within a chondromyxoid matrix (Arch Pathol Lab Med 2001;125:1224)

Cytology images
=========================================================================



Multiple fragments with focal adipose differentiation and chondroid myxoid appearance

Positive stains
=========================================================================

● S100 (mature adipocytes stain stronger than lipoblasts) and vimentin, PAS+ glycogen, Alcian blue and toluidine blue (stain chondroitin substrate)
● Variable focal CD68 and keratin (Hum Pathol 1995;26:706)
● Collagen IV reactivity around tumor cells
● High expression of cyclin d1 (Sarcoma 2011;2011:638403)

Negative stains
=========================================================================

● EMA, HMB45, smooth muscle actin, Ki-67 (or low)

Electron microscopy description
=========================================================================

● Abundant intracytoplasmic lipid and glycogen and numerous pinocytotic vesicles, characteristic of white adipocytes (Am J Surg Pathol 1995;19:1272)
● Resembles embryonal fat, and to a lesser extent, embryonal cartilage
● Cells have knob like protrusions of cell membrane containing granular, amorphous and fibrillar material
● No prominent mitochondria, no lysosomes (Hum Pathol 1995;26:706)

Molecular/cytogenetics description
=========================================================================

● t(11;16) - also in hibernoma (Am J Surg Pathol 1999;23:1300, Mod Pathol 1999;12:88)

Cytogenetics images
=========================================================================



t(11;16) plus other changes

Differential diagnosis
=========================================================================

Lipoma with chondroid metaplasia: true cartilage present
Extraskeletal chondroma: distal extremities, mature hyaline cartilage, no fat
Extraskeletal myxoid chondrosarcoma: prominent fibrous septa; chondroblasts typically lack intracytoplasmic vacuoles, no mature fat; frequently has mitotic figures and necrosis
Mixed tumor: foci of epithelial differentiation, keratin+, no lipoblasts
Myxoid liposarcoma: different sites, usually no prominent cords or clusters of cells; has delicate plexiform capillary matrix, t(12;16)

Additional references
=========================================================================

Radiographics 2004;24:1433, Stanford University, Ann Diagn Pathol 2012;16:230



Adipose tissue

Fibrolipoma


Reviewer: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 10 November 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Lipoma with prominent bundles of mature fibrous tissue traversing fatty lobules

Terminology
=========================================================================

● Not a WHO diagnosis
● Fibrovascular polyps of esophagus are also called fibrolipomas
● See also lipomatosis of nerve

Sites
=========================================================================

● Common in neck
● Also present in head and neck (Contemp Clin Dent 2012;3:S112)

Case reports
=========================================================================

● 48 year old woman with giant fibrolipoma of leg (Anticancer Res 2006;26:3649)
● 71 year old woman with 9 cm fibrolipoma of parotid gland (World J Surg Oncol 2006;4:28)

Clinical images
=========================================================================



Intraoperative parotid tumor

Gross images
=========================================================================



Encapsulated mass

Micro description
=========================================================================

● Lipoma with fibrous tissue component

Micro images
=========================================================================



Mature adipose tissue and dense bands of fibrosis


Mature adipose tissue and fibrous tissue


Myxoid change

Differential diagnosis
=========================================================================

Spindle cell lipoma: shoulders/back, CD34+ bland spindle cells, pleomorphic cells
Lipoma of hands, feet or buttocks: typically has dense fibrous tissue
Well differentiated liposarcoma: atypical cells present in fibrous areas



Adipose tissue

Intramuscular lipoma


Reviewer: Charanjeet Singh, M.D. (see Reviewerspage)
Revised: 10 November 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Lipoma that infiltrates within muscle belly
● Called intermuscular lipoma if between muscle fascicles

Terminology
=========================================================================

● Also called invasive or infiltrative lipoma
● Not a WHO diagnosis

Sites
=========================================================================

Intramuscular: affects thigh, trunk, head and neck of middle-aged adults
Intermuscular: affects abdominal wall of middle-aged adults; doesn’t recur if completely excised

Clinical features
=========================================================================

● Benign, but 20% recur due to incomplete excision
● Infiltration may be due to muscular degeneration and endomysial fatty growth secondary to atrophy (BMC Musculoskelet Disord 2004;18:20)

Case reports
=========================================================================

● 37 year old woman with giant infiltrative tumor of face (AJNR Am J Neuroradiol 2003;24:283)
● 58 year old and 63 year old women with tumors of pectoralis major muscle simulating a breast mass (Ann Acad Med Singapore 2005;34:275, Arch Pathol Lab Med 2011;135:1061)
● Well circumscribed tumor of sternocleidomastoid muscle (Auris Nasus Larynx 2004;31:283)

Clinical images
=========================================================================



Tumor of face

Gross description
=========================================================================

Intramuscular - poorly circumscribed, extends between and around skeletal muscle fibers

Gross images
=========================================================================



Yellow adipose tissue within skeletal muscle


Irregular lobulated tumor without encapsulation


Deep tumor of calf

Other images: yellow adipose tissue within skeletal muscle

Micro description
=========================================================================

● Mature lipocytes that infiltrate skeletal muscle
● No atypia, no mitotic figures

Micro images
=========================================================================



Prominent muscular atrophy


Adipocytes and atrophic muscle


Intramuscular lipoma

Other images: intramuscular fat tissue covered by fibrous capsule

Differential diagnosis
=========================================================================

Intramuscular hemangioma: adolescents and young adults, usually head and neck, prominent vasculature, variable adipose tissue
Well differentiated liposarcoma: definite atypia present



Adipose tissue

Lipoma arborescens


Reviewer: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 11 November 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Fatty infiltration of subsynovial connective tissue in a large joint
● Rarely affects synovial sheaths of tendons (J Am Podiatr Med Assoc 2009;99:153)

Terminology
=========================================================================

● Also called villous lipomatous proliferation of synovial membrane, diffuse lipoma of joint
● Not a WHO diagnosis

Epidemiology
=========================================================================

● Rare
● Older patients, usually male, associated with joint trauma, degenerative joint disease and chronic arthritis

Clinical features
=========================================================================

● Usually knee
● May be a reactive process
● MRI is useful in diagnosis (Radiol Med 2005;109:540)

Case reports
=========================================================================

● 24 year old man with multifocal lipoma arborescens (Skeletal Radiol 2005;34:536)
● Bilateral knee involvement (Knee 2005;12:394)

Treatment and prognosis
=========================================================================

● Synovectomy
● May recur since often is a reactive process

Gross description
=========================================================================

● Yellow fat in villous fronds

Gross images
=========================================================================



Villous lesion in knee

Micro description
=========================================================================

● Hypertrophic villous projections of fat lined by synovial cells, variable scattered inflammatory cells

Micro images
=========================================================================



Various images

Additional references
=========================================================================

Stanford University, Ann Saudi Med 2011;31:194



Adipose tissue

Lipoma of tendon sheath


Reviewer: Charanjeet Singh, M.D. (see Reviewerspage)
Revised: 11 November 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Lipoma attached to tendon

Terminology
=========================================================================

● Not a WHO diagnosis
● May be a variant of lipoma arborescens

Epidemiology
=========================================================================

● Very rare
● Adults age 40 years or less (Radiographics 2004;24:1433)

Sites
=========================================================================

● Tendons of hands and wrist
● Less often ankle and foot

Case reports
=========================================================================

● Causing carpal tunnel syndrome (Orthop Rev 1988;17:1083)
● Causing quadriceps tendon rupture (Cir Cir 2008;76:259)

Gross description
=========================================================================

● Focal lipomatous mass resembling lipoma

Micro description
=========================================================================

● Resembles lipoma, but adherent to tendon or intersecting its fibers

Micro images
=========================================================================



Tendon lipoma

Differential diagnosis
=========================================================================

Lipoma arborescens: usually not a discrete mass, affects knee, not hands/wrist



Adipose tissue

Lipomatosis


Reviewer: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 21 December 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

See also pelvic lipomatosis

General
=========================================================================

● Diffuse overgrowth of mature adipose tissue

Epidemiology
=========================================================================

● Rare disorder of children under 2 years or adults
● Associated with obesity, Cushing’s disease, steroid therapy, protease inhibitors for HIV
● Familial multiple lipomatosis: rare, usually autosomal dominant; multiple lipomas of trunk and extremities with relative sparing of the head and shoulders; due to translocation involving high-mobility-group protein isoform I-C on chromosome 12 and the lipoma preferred partner gene on chromosome 3 (An Bras Dermatol 2012;87:324)
● See also below - adiposis dolorosa, multiple symmetric lipomatosis

Sites
=========================================================================

● Limb (may cause massive enlargement) or trunk

Case reports
=========================================================================

● Infiltrating lipomatosis in face of child (J Plast Reconstr Aesthet Surg 2009;62:e561)
● Causing mediastinal widening on chest Xray of morbidly obese woman (Cases J 2008 Sep 19;1:171)
● 89 year old man with familial disease (Dermatol Online J 2003;9:9)
● Familial disease with normal karyotype (Cutis 2007;79:227)

Treatment and prognosis
=========================================================================

● Palliative surgical removal of excess fat
● May recur
● May lead to amputation of extremity due to distortion or loss of function

Clinical images
=========================================================================



Familial multiple lipomatosis: lesions of abdomen and arms

Gross description
=========================================================================

● Poorly circumscribed aggregates of normal appearing fat in subcutaneous and skeletal muscle (but not confined to muscle)
● Does not affect nerves

Micro description
=========================================================================

● Sheets and lobules of white adipose tissue that may infiltrate skeletal muscle
● May involve bone

Micro images
=========================================================================



Lipomatosis infiltrating skeletal muscle

Positive stains
=========================================================================

● S100, vimentin

Additional references
=========================================================================

Stanford University


Adiposis dolorosa (subtopic of lipomatosis)

General
=========================================================================

● Tender accumulations of subcutaneous fat / lipomas, often in pelvis and lower extremities of postmenopausal women

Terminology
=========================================================================

● Also called Dercum’s disease

Epidemiology
=========================================================================

● Associated with women, obesity, hypercholesterolemia

Clinical features
=========================================================================

● Pain may be due to pressure of fat / lipomas on peripheral nerves

Case reports
=========================================================================

● 51 year old obese woman with multiple painful subcutaneous lipomas (Ann Ital Med Int 2005;20:187)
● 63 year old obese woman with recurrent abdominal pain treated medically (Dtsch Med Wochenschr 2006;131:434)

Clinical images
=========================================================================



Type I Dercum’s disease: generalised diffuse form with widespread painful adipose tissue but no distinct lipomas

Additional references
=========================================================================

eMedicine, OMIM 103200, Orphanet J Rare Dis 2012;7:23


Multiple symmetric lipomatosis (subtopic of lipomatosis)

General
=========================================================================

● Multiple non-encapsulated lipomas with symmetric distribution and sparing of distal arms and legs

Terminology
=========================================================================

● Also called Madelung’s disease, Launois-Bensaude syndrome, benign symmetric lipomatosis

Epidemiology
=========================================================================

● Rare, usually men, ages 40+ years
● Associated with high ethanol intake (Int J Obes Relat Metab Disord 2002;26:253)
● Women: more common in proximal arms (91%) and legs (54%); also associated with high ethanol intake (Int J Obes Relat Metab Disord 2003;27:1419)

Treatment and prognosis
=========================================================================

● Associated with significant morbidity, including metabolic disturbances, neuropathy, malignancy and sudden death
● Treatment - liposuction or surgery, not diet (Acta Dermatovenerol Croat 2008;16:31)
● Possibly fibrate drugs (Obes Surg 2008;18:240) or intralesional injections (Aesthetic Plast Surg 2010;34:153)

Case reports
=========================================================================

● 8 year old girl with bilateral neck swellings (Dentomaxillofac Radiol 2007;36:51)
● 49 year old woman post-liver transplant for cirrhosis (Dermatology 2008;216:337)

Gross description
=========================================================================

● Involves subcutaneous and deep soft tissue

Gross images
=========================================================================



Neck tumor

Clinical images
=========================================================================



Multiple neck masses


Various images

Micro description
=========================================================================

● Unencapsulated masses of mature adipose tissue

Micro images
=========================================================================



Resembling well differentiated liposarcoma


Adipose surrounding nerve

Molecular/cytogenetics description
=========================================================================

● May be associated with mitochondrial DNA abnormalities (Neurology 1994;44:862)

Additional references
=========================================================================

OMIM 151800



Adipose tissue

Lipomatosis of nerve


Reviewer: Charanjeet Singh, M.D. (see Reviewerspage)
Revised: 11 November 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Infiltration of epineurium of a major nerve by adipose and fibrous tissue

Terminology
=========================================================================

● Also called fibrolipoma of nerve, fibrolipomatous hamartoma of nerve, macrodystrophia lipomatosa

Epidemiology
=========================================================================

● May be noted at birth
● Almost always age 30 years or less
● Associated with macrodactyly (abnormal enlargement of digits) innervated by affected nerve in 30-67%

Sites
=========================================================================

● 85% have involvement of median nerve and its digital branches in hand, wrist and forearm (Histopathology 1994;24:391)
● Also ulnar nerve

Radiology
=========================================================================

● T1 weighted images on MR imaging reveal a fatty mass that is evenly distributed between nerve bundles and is seen running along individual nerves
● Often described as having a “coaxial cable-like” appearance on axial scans (Acta Radiol 2003;44:326)

Case reports
=========================================================================

● 26 year old man with sciatic nerve involvement (Microsurgery 2009;29:66)
● 26 year old man with mass on palm of hand (Case of the Week #158)
● 32 year old woman (J Orthop Surg (Hong Kong) 2011;19:123)
● 46 year old man with bilateral involvement (Muscle Nerve 1998;21:656)

Treatment and prognosis
=========================================================================

● Benign but often no effective treatment as resection causes sensory and motor deficits (J Neurosurg 1998;89:683)
● Carpal tunnel release may relieve symptoms of median nerve involvement
● Amputation if severe deformity
● May recur in 33-60% if incomplete resection

Gross description
=========================================================================

● Fusiform enlargement of nerve by yellow adipose tissue, confined within epineurium

Clinical images
=========================================================================



Lipomatosis of median nerve with macrodactyly


Thickened median nerve

Gross images
=========================================================================



Excised tissue with macrodactyly

Micro description
=========================================================================

● Infiltration of epineurium and perineurium by adipose and fibrous tissue (collagen), causing enlargement of nerve
● Concentric perineurial fibrous tissue and pseudo-onion bulb formation
● Occasionally metaplastic bone

Micro images
=========================================================================



Tumor of second digit


With osseous and soft-tissue hypertrophy and predominance of fat


Lipomatous infiltration around nerve fascicles


Case of the Week #158


Lipoma of nerve

Differential diagnosis
=========================================================================

Intraneural lipoma: mass of fatty tissue displaces nerve bundles, but does not separate them
Diffuse lipomatosis: not confined to epineurium
Traumatic neuroma: onion bulb formation, usually lacks concentric perineural fibrosis, has high T2 signal density on magnetic resonance imaging

Differential diagnosis of macrodactyly
=========================================================================

● Angiomatosis
Neurofibromatosis type 1
● Klippel-Trenaunay-Weber syndrome (eMedicine)
● Proteus syndrome (Wikipedia)



Adipose tissue

Lumbosacral lipoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Diffuse overgrowth of mature fat overlying lumbosacral spine

Terminology
=========================================================================

● Not a WHO diagnosis

Epidemiology
=========================================================================

● Infants and children (incidence of 4-8 per 100K population), peaks at ages 0-2 and 7-8 years
● Associated with spina bifida or laminar defect
● Usually connected to spinal cord or cauda equina through defect

Case reports
=========================================================================

● Child born at 37 weeks (Neurol Med Chir (Tokyo) 2009;49:487)

Micro description
=========================================================================

● May contain numerous vessels or smooth muscle cells

Additional references
=========================================================================

Childs Nerv Syst 2002;18(:326, Pediatr Neurosurg 2001;34:124



Adipose tissue

Myolipoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Benign tumor of mature adipocytes and mature smooth muscle
● First described in 1991 (Am J Surg Pathol 1991;15:121)

Terminology
=========================================================================

● Called lipoleiomyoma in uterus
● Note: myelolipoma is tumor with hematopoietic (including myeloid) elements, often in adrenal gland

Epidemiology
=========================================================================

● Very rare tumor of adults in abdomen, retroperitoneum or abdominal wall
● Other rare sites include eyelid, pericardium, base of tongue

Case reports
=========================================================================

● 4 year old boy presented with paraspinal tumor (Case Report Med 2009;2009:520126)
● 34 year old woman with tumor of iliac fossa (World J Surg Oncol 2005;3:72)
● 55 year old woman with tumor presenting as inguinal hernia (Radiology Case Reports 2006, Vol 1, No 1)

Treatment and prognosis
=========================================================================

● Excision
● Does not recur, metastasize or transform

Gross description
=========================================================================

● Often 9 cm or more, completely or partially encapsulated, yellow-white

Gross images
=========================================================================



Large lobulated mass with thick pseudocapsule


Fatty tissue with bands and nodules of firm white tissue

Micro description
=========================================================================

● Mature adipose tissue and mature (well differentiated) smooth muscle in short fascicles (Stanford University)
● Variable fibrosis and inflammation
● No floret cells, no thick walled vessels, no necrosis, no mitotic figures

Micro images
=========================================================================



Mature fat and smooth muscle fibers


Smooth muscle fibers are SMA+ (left), desmin+ (right two images)

Positive stains
=========================================================================

● Smooth muscle actin, desmin
● Occasionally ER, PR

Differential diagnosis
=========================================================================

Angiomyolipoma: also thick walled vessels, HMB45+
Liposarcoma with heterologous elements: has lipoblasts and atypia
Low grade leiomyosarcoma infiltrating fat: smooth muscle component has atypia and mitotic figures, adipose tissue is not part of tumor



Adipose tissue

Myxoid lipoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Lipoma with well developed myxoid areas

Terminology
=========================================================================

● Also called myxolipoma
● Not a WHO diagnosis

Epidemiology
=========================================================================

● Uncommon
● Some cases may actually be spindle cell lipomas (Am J Dermatopathol 2006;28:28)

Case reports
=========================================================================

● 57 year old man with tender elbow mass (J Med Case Rep 2011;5:321)

Micro description
=========================================================================

● Lipoma with well developed myxoid areas
● No atypia, no plexiform vascular network, no lipoblasts

Micro images
=========================================================================



Adipocytes interspersed with deposition of mucin, and myxoid change

Positive stains
=========================================================================

● Oil Red O (strong cytoplasmic staining on frozen tissue)
● Mucoid material: PAS+ diastase resistant, Alcian Blue+

Electron microscopy description
=========================================================================

● Adipocytes in various stages of differentiation with mature cells surrounded by basal lamina, lipid globules of varying size, pinocytotic vesicles in plasma membrane (Oral Surg Oral Med Oral Pathol 1984;57:300)

Differential diagnosis
=========================================================================

Myxoid liposarcoma: not in subcutaneous tissue, no classic lipoma areas, has lipoblasts and plexiform vascular pattern



Adipose tissue

Nevus lipomatosus superficialis


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Nodules of mature fat tissue within dermis
● Either solitary or multiple

Terminology
=========================================================================

● Also called nevus lipomatosus cutaneous superficialis and dermolipoma
● Not a WHO diagnosis
● First described in 1921 by Hoffman and Zurhelle
● Considered to be a developmental anomaly or hamartoma

Epidemiology
=========================================================================

● Uncommon
● At birth or by age 20 years

Clinical features
=========================================================================

● Buttocks or upper thighs
● Either solitary (more common) or multiple type of Hoffmann-Zurhelle (Tunis Med 2006;84:800)

Case reports
=========================================================================

● 7 year old girl with congenital lesion of calf (J Postgrad Med 2005;51:47)
● 12 year old girl with neck lesion (Indian J Dermatol Venereol Leprol 2006;72:66)
● 33 year old man with slow growing cutaneous plaque of lumbar region (Patholog Res Int 2011;2011:105973)
● 35 year old woman with thigh lesion (Archives of Iranian Medicine)
● 45 year old man with lower back lesion (Indian J Dermatol Venereol Leprol 1994;60:39)
● 51 year old man with lesion on pinna for 15 years (Dermatol Online J 2010;16:12)

Treatment and prognosis
=========================================================================

● Excision - does not recur

Clinical images
=========================================================================



Lumbar region


Pinna lesion


Brown-red nodules

Gross description
=========================================================================

● Soft yellow papules

Micro description
=========================================================================

● Mature adipocytes in dermis
● No encapsulation or connection with subcutaneous fat
● No distinct epidermal changes

Micro images
=========================================================================



Dermal adipose tissue is continuous with underlying subcutis


Ectopic fat in mid to lower dermis




Various images

Differential diagnosis
=========================================================================

Fibroepithelial polyp
Neurofibroma
Nevus sebaceous



Adipose tissue

Pelvic lipomatosis


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Lipomatosis in region of rectum or bladder, rarely in retroperitoneum (Stanford University)
● Also occurs in renal hilum, associated with chronic pyelonephritis, renal lithiasis and kidney atrophy
● Not a WHO diagnosis

Epidemiology
=========================================================================

● Rare
● Usually black men, median age 48 years, range 9-80 years
● Present with urological or digestive symptoms
● Associated with cystitis glandularis, cystitis cystica or cystitis follicularis in 75% of cases; may develop adenocarcinoma

Case reports
=========================================================================

● 32 year old hypertensive man with bilateral obstructive uropathy (Urol Int 2010;84:239)
● 51 year old man with painless hematuria (Incont Pelvic Floor Dysfunct 2008;2:124 (pdf))
● 58 year old man with bladder adenocarcinoma (Urol Oncol 2004;22:428)
● 70 year old man with gross hematuria and bilateral hydronephrosis (Nihon Hinyokika Gakkai Zasshi 2007;98:37)
● Two brothers with renal failure (Beijing Da Xue Xue Bao 2007;39:355)

Gross images
=========================================================================



Kidney shows increase in peripelvic adipose tissue, hydronephrosis and cortical atrophy

Micro description
=========================================================================

● Normal adipose tissue

Micro images
=========================================================================



Unremarkable adipose tissue


Associated cystitis glandularis

Differential diagnosis
=========================================================================

Well differentiated liposarcoma: discrete mass, not in pelvis, atypical cells within fibromyxoid stroma



Adipose tissue

Pleomorphic lipoma / spindle cell lipoma - general


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Subcutaneous tumor of back, shoulder or posterior neck with mature adipocytes, bland spindle cells, floret cells and collagen (Stanford University)

Epidemiology
=========================================================================

● Pleomorphic lipoma and spindle cell lipoma represent a continuum of benign tumors - most tumors show some features of both
● 70% occur in subcutaneous tissue of shoulder, back and posterior neck
● 90% men
● Usually ages 45-65 years
● Usually relatively superficial
● If deep, some suggest calling well differentiated liposarcoma

Treatment and prognosis
=========================================================================

● Excision
● Only rare local recurrences, no metastases

Gross description
=========================================================================

● Usually 3-5 cm, well circumscribed, yellow-gray-white, firmer than classic lipoma

Molecular/cytogenetics description
=========================================================================

● 16q or 13q abnormalities in 70%
● Frequently hypodiploid


Pleomorphic lipoma

General
=========================================================================

● Mature adipocytes, dense collagen and floret giant cells in subcutaneous tissue of neck, back or shoulder
● Usually dermal or beneath mucous membranes

Epidemiology
=========================================================================

● Rare - incidence is only 10% that of spindle cell lipoma

Treatment and prognosis
=========================================================================

● Excision, only rarely recurs

Micro description
=========================================================================

● Circumscribed tumor with adipocytes that are variable in size at low power
● Prominent floret giant cells (hyperchromatic, multinucleated, wreath like nuclei) and small round hyperchromatic cells
● May have spindle cells similar to spindle cell lipoma
● No/rare lipoblasts, no prominent vascularity

Micro images
=========================================================================



Numerous pleomorphic and floret cells


Various images

Other images: pleomorphic lipoma

Cytology description
=========================================================================

● Atypical large and floret cells with background of mature adipocytes (Diagn Cytopathol 2005;32:110)
● Cells may appear malignant (Acta Cytol 2000;44:255, Diagn Cytopathol 2010;38:184)

Positive stains
=========================================================================

● CD34, vimentin

Negative stains
=========================================================================

● Keratin, S100 (fat cells are S100+), CD68, desmin, smooth muscle actin

Differential diagnosis
=========================================================================

Neurofibroma: may have floret cells (Diagn Pathol 2007;2:47)
Well differentiated liposarcoma: deep location, more lipoblasts, variable thick collagen, variable floret giant cells, CD34-


Spindle cell lipoma

General
=========================================================================

● Mature adipocytes, bland spindle cells with wispy eosinophilic cytoplasm in subcutaneous tissue of neck, back or shoulder (Stanford University)

Epidemiology
=========================================================================

● Rarely are multiple tumors (Am J Surg Pathol 1998;22:40)

Case reports
=========================================================================

● 51 year old woman with hypopharyngeal tumor (Int J Med Sci 2011;8:479)
● 53 year old man with intramuscular tumor of face (J Cutan Pathol 2009;36:70)
● 55 year old man with neck mass (Case of the Week #182)
● 63 year old man with supraclavicular mass (Int J Otolaryngol 2010;2010:942152)

Treatment and prognosis
=========================================================================

● Excision, only rarely recurs (Cancer 1975;36:1852)

Gross images
=========================================================================



Fatty (F) and hemorrhagic (H) tumor


Yellow tumor due to numerous adipocytes

Micro description
=========================================================================

● Mixture of mature adipocytes and bland spindle cells (pale eosinophilic cytoplasm with uniform wavy nuclei similar to neurofibroma) in mucinous / myxoid or fibrous background with thick collagen bundles
● Spindle cells are arranged in short fascicles with occasional nuclear palisading
● May have hemangiopericytic or angiomatous vascular pattern (Pathol Int 2007;57:26)
● May have minimal/no fat (Am J Dermatopathol 2007;29:437)
● Variable mast cells and lymphocytes
● No storiform pattern, no lipoblasts, no/rare mitotic activity

Micro images
=========================================================================



Adipocytes, spindle cells and ropy collagen


Hemangiopericytic vascular pattern


Pseudoangiomatous appearance


Spindle cells have inconspicuous cytoplasm and small, slender, uniform nuclei


Spindle cells and collagen with few adipocytes




Various images


Various images

Cytology description
=========================================================================

● Scattered clusters of mildly pleomorphic spindle cells mixed with mature adipocytes, mast cells and small collagen fragments (Diagn Cytopathol 2000;23:362)

Cytology images
=========================================================================



Breast tumor: H&E and CD34

Positive stains
=========================================================================

Spindle cells - CD34, androgen receptors in men and usually women (Arch Pathol Lab Med 2008;132:81)
Adipocytes - S100

Negative stains
=========================================================================

Spindle cells - S100, desmin

Electron microscopy description
=========================================================================

● Spindled non-fat storing mesenchymal cells and mature lipocytes (Am J Surg Pathol 1981;5:435)

Molecular/cytogenetics description
=========================================================================

● Usually 16q abnormalities

Differential diagnosis
=========================================================================

Cellular angiofibroma: vascular tumor, but similar cytogenetics (Cancer Genet Cytogenet 2007;177:131)
Lipomatous hemangiopericytoma: staghorn vascular pattern
Myxoid liposarcoma: lipoblasts and pleomorphic spindle cells, prominent plexiform vascular pattern, no thick collagen bundles, CD34-
Neurofibroma: different morphology, no prominent adipose, strongly S100+
Schwannoma: different morphology, no prominent adipose, strongly S100+
Solitary fibrous tumor: patternless pattern, thin collagen fibers, no prominent adipose, CD99+, bcl2+, CD34+



Adipose tissue

Hemosiderotic fibrohistiocytic lipomatous lesion


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 5 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Superficial benign fatty lesion, usually of foot/ankle, with CD34+ spindle cells and abundant hemosiderin
● Possibly a reactive lesion
● Not a WHO diagnosis

Epidemiology
=========================================================================

● Rare (10 per 6000 lipomas), usually women, mean age 51 years (range, 42-63 years)
● Usually feet and ankle region, rarely cheeks, hands, calf, thigh
● Associated with trauma (70%); may be reactive (Mod Pathol 2000;13:1192)
● Associated with venous stasis (Virchows Arch 2005;447:103)
● May be related to early pleomorphic hyalinizing angiectatic tumor (Pathol Int 2006;56:283, Am J Surg Pathol 2004;28:1417)

Case reports
=========================================================================

● 33 year old woman with knee tumor (Sao Paulo Med J 2009;127:174)
● 44 year old woman with recurring foot lesion (Case of the Week #199)
● 55 year old woman with swelling of hand (Malaysian J Pathol 2011;33:43 (pdf))
● 56 year old woman with foot mass for 10 years (Clin Orthop Relat Res 2010;468:2808)
● 66 year old man with thigh lesion (Sarcoma 2008;2008:893918)

Treatment and prognosis
=========================================================================

● Radical surgical excision and follow up
● May recur locally
● No metastases or deaths

Gross description
=========================================================================

● Mean 8 cm (range, 2-17 cm), solid and circumscribed but not encapsulated

Micro description
=========================================================================

● Unencapsulated circumscribed superficial fatty lesion with CD34+ spindle cells and abundant hemosiderin (Stanford University)
● Spindle cells have vesicular nuclei and indistinct nucleoli with occasional hyperchromatism
● Inflammatory background
● No/minimal atypia

Micro images
=========================================================================







Various images






Case of the Week #199

Positive stains
=========================================================================

● CD34, vimentin, calponin

Negative stains
=========================================================================

● S100, desmin



Adipose tissue

Hibernoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 11 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Lipoma containing prominent brown adipocytes that resembles normal brown fat as classic lipoma resembles white fat

Epidemiology
=========================================================================

● Rare (2% of lipomas)
● Mean age 26-38 years; 60% male

Sites
=========================================================================

● Most commonly in axilla, back, mediastinum, shoulder, thigh (Am J Surg Pathol 2001;25:809); also abdominal cavity, arm, breast, paraglottic space, parasacral region, retroperitoneum, spermatic cord

Clinical features
=========================================================================

● May produce steroid hormones

Case reports
=========================================================================

● 3 month old (Arch Argent Pediatr 2011;109:126)
● 12 year old girl with symptomatic tumor (J Pediatr Hematol Oncol 2008;30:900)
● 25 year old man with mediastinal tumor (J Clin Pathol 2004;57:993)
● 35 year old woman with vulvar tumor (Indian J Pathol Microbiol 2011;54:817)
● 39 year old man with 9 cm thigh mass (Case of the Week #245)
● 52 year old woman with mediastinal tumor (Interact Cardiovasc Thorac Surg 2011;12:845)
● 2 hibernomas with p53 overexpression (Arch Pathol Lab Med 2002;126:975)

Treatment and prognosis
=========================================================================

● Excision
● May recur if incompletely excised

Clinical images
=========================================================================



Supraclavicular tumor

Gross description
=========================================================================

● Mean 9 cm, red/brown cut surface, soft, lobulated, well delineated or encapsulated
● 10% infiltrate adjacent striated muscle
● Brown color may be due to vascularity or mitochondria
● Resembles brown fat in some hibernating animals

Gross images
=========================================================================



Left to right: tumors of thigh, neck, axilla, vulva

Other images: Gluteal tumor

Micro description
=========================================================================

● Organoid arrangement of uniform large cells resembling brown fat with coarsely granular to multivacuolated cytoplasm that is eosinophilic or pale
● Vacuoles are small and stain for neutral fat
● Nucleus is small, central with no/rare atypia
● Often mixtures of white fat
● May have loose basophilic matrix, features of spindle cell lipoma (if in neck/scalp), only scattered hibernoma cells
Subtypes: classic, lipoma-like, myxoid (Ann Diagn Pathol 2006;10:104), spindle cell (CD34+)

Micro images
=========================================================================



Lobulated pattern




Granular to multivacuolated cytoplasm


Mixed with white fat


Vascular changes


Left to right: neck, pleural, mediastinal and vulvar tumors


Multivacuolated tumor cells are S100+


CD31+

Cytology description
=========================================================================

● Small, round, brown fat-like cells with uniform, small cytoplasmic vacuoles and regular, small, round nuclei
● Delicate branching capillaries
● Variable mature fat cells (Cancer 2001;93:206)

Positive stains
=========================================================================

● S100 (85%), Oil Red O and Sudan Black, CD31 (Arch Pathol Lab Med 2006;130:480)
● Also uncoupling protein 1 / UCP-1

Negative stains
=========================================================================

● CD34 (usually), p53 (usually, but see case report above)

Electron microscopy description
=========================================================================

● Resembles brown fat
● Each tumor cell is invested by a basal lamina
● Inverse relationship exists between lipid droplet size and the number of mitochondria per unit of cytoplasm
● Pleomorphic mitochondria with dense matrices or large round mitochondria with transverse lamellar cristae
● Undulating plasmalemmal invaginations, micropinocytotic vesicles, periodic short plasmalemmal densities
● Conspicuous lack of cytoplasmic membrane systems (Hum Pathol 1983;14:677)

Molecular/cytogenetics description
=========================================================================

● 11q13-21 rearrangements (also seen in lipomas and liposarcomas)

Differential diagnosis
=========================================================================

Liposarcoma-well differentiated: tumors are deep, have atypia and specific translocations
Lipoma (classic): lipocytes are not multivacuolated
Residual brown fat around cervical or axillary lymph nodes: seen in children, not a distinct mass

Additional references
=========================================================================

Stanford University



Adipose tissue

Lipoblastoma / lipoblastomatosis


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 11 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Lobulated tumor, either localized (lipoblastoma) or diffuse (lipoblastomatosis), resembling fetal adipose tissue

Terminology
=========================================================================

Lipoblastoma: also called fetal/embryonal lipoblastoma; well circumscribed and subcutaneous
Lipoblastomatosis: deep-seated and ill-defined

Epidemiology
=========================================================================

● Rare
● Infants and young children age 3 years or less (rarely ages 14-24 years)
● 80% are boys

Sites
=========================================================================

● Extremities, trunk, head and neck
● Occasionally mediastinum, retroperitoneum or inguinal region, thigh, parotid region, scrotum, intrathoracic region

Clinical features
=========================================================================

● Usually presents as painless superficial soft tissue mass, 75% on left side
● If not removed, matures into lipoma but with prominent fibrous septa
● FISH is helpful to confirm diagnosis (Histopathology 2008;52:294)

Case reports
=========================================================================

● 10 month old girl with 17 cm omental tumor (J Pediatr Surg 2007;42:1149)
● 1 year old boys with cervical mass (Case of the Week #123), scrotal tumor (Arch Pathol Lab Med 2004;128:797), thigh mass (J Cancer Res Ther 2012;8:157), thoracic cavity / mediastinal tumor (Rare Tumors 2011;3:e51)
● 18 month old boy with intraabdominal mass (Afr J Paediatr Surg 2011;8:320)
● Buttock lesions (J Pediatr Orthop B 2006;15:356)

Treatment and prognosis
=========================================================================

● Complete excision, but with sparing of neurovascular bundle in large tumors (J Pediatr Surg 2008;43:1295)
● 14% recur due to incomplete removal (particularly lipoblastomatosis, Am J Surg Pathol 1997;21:1131)
● Does not metastasize
● Follow up for 3+ years is recommended (Pediatr Surg Int 2005;21:809)

Gross description
=========================================================================

● Soft, lobulated
● Usually 2-5 cm, mucoid cut surface

Clinical images
=========================================================================



Lobulated and encapsulated tumor

Gross images
=========================================================================



Various images

Micro description
=========================================================================

● Hypocellular lobules of adipocytes in various stages of differentiation including preadipocytes (spindle or stellate shaped), uni- or multi-vacuolated lipoblasts and mature adipocytes in central lobule
● Separated by prominent fibrous septa that may be cellular
● Has plexiform vascular pattern and abundant myxoid stroma
● May have prominent extracellular mucinous pools
● Resembles fetal fat and myxoid liposarcoma
Lipoblastomatosis: less lobulation; infiltrates skeletal muscle

Micro images
=========================================================================



Lobular architecture with prominent fibrous septa


Plexiform vascular pattern with myxoid matrix and small fat cells


Resembles lipoma with minimal myxoid stroma


Various images


1 year old boy with neck mass


Scrotal tumor

Other images: scapula tumor #1; #2; #3; #4

Cytology description
=========================================================================

● Moderate to poorly cellular
● Clusters of lipocytes, lipoblasts, spindle cells
● Background of myxoid material and naked oval nuclei (Diagn Cytopathol 2005;33:195)

Cytology images
=========================================================================



1 year old boy with neck mass

Electron microscopy description
=========================================================================

● Cells have investing basal lamina, pinocytotic vesicles, Golgi membranes, round/oval mitochondria, cytoplasmic glycogen and cytoplasmic lipid (Am J Surg Pathol 1980;4:163)
● Resembles myxoid liposarcoma and normal developing fat

Electron microscopy images
=========================================================================



Primitive lipoblast has high nuclear-cytoplasmic ratio, intracytoplasmic lipid droplets, few organelles

Molecular/cytogenetics description
=========================================================================

● Rearrangement of 8q11 approximately q13 region in 82% (Cancer Genet Cytogenet 2008;183:60), includes PLAG1 gene (Am J Pathol 2001;159:955)
● Produces HAS2-PLAG1 and COL1A2-PLAG1 hybrid genes (Atlas of Genetics and Cytogenetics)
● Also polysomy for chromosome #8
● t(3;8)(p13;q21.1) also described (Pediatr Surg Int 2012;28:737)

Molecular/cytogenetics images
=========================================================================



FISH / CISH of PLAG1 gene

Differential diagnosis
=========================================================================

Lipofibromatosis / infantile fibromatosis: fibrous tissue only but may entrap mature fat cells, no myxoid stroma, no plexiform vascular pattern
Myxoid liposarcoma: rare in children, no distinct lobulation, usually more cellular with giant cells containing pleomorphic nuclei, different molecular abnormalities
Well differentiated liposarcoma: rare in children, has mature fat but no lipoblasts, has spindle cells with large, deep-staining nuclei and marked nuclear enlargement or pleomorphism; low cellularity, MDM2 and CDK4 immunostains are sensitive and specific (Am J Surg Pathol 2005;29:1340)

Additional references
=========================================================================

Stanford University



Adipose tissue

Subconjunctival herniated orbital fat


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 11 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Prolapse of subconjunctival intraconal orbital fat
● First described in pathology literature in 2007 (Am J Surg Pathol 2007;31:193)
● Not a WHO diagnosis

Clinical features
=========================================================================

● Rarely causes an intraorbital mass lesion
● Mean age 66 years, 90% men
● Prolapse is usually into superotemporal quadrant or lateral canthus
● Usually due to orbital fat herniation through a dehiscence in Tenon's capsule
● Manifests as unilateral or bilateral yellowish mass
● Does not recur

Case reports
=========================================================================

● Infant with small yellow mass in right eye (Eur J Pediatr 2010;169:1427)
● 52 year old woman with inferonasal mass (Nihon Ganka Gakkai Zasshi 2008;112:1085)

Clinical images
=========================================================================



Various images

Micro description
=========================================================================

● Mature fat, fibrous septa without hyperchromatic cells
● Adipocytes with intranuclear vacuoles (Lochkern cells) and floret cells (multinucleated giant cells with wreath like pattern of normal nuclei)
● Variable histiocytes, lymphocytes, plasma cells and mast cells

Positive stains
=========================================================================

Floret cells - CD34 and vimentin
Lochkern cells - CD34, vimentin and S100

Differential diagnosis
=========================================================================

Pleomorphic lipoma: different clinical presentation; aggregates of bland spindle cells, floret cells and wiry collagen
Well differentiated liposarcoma: different clinical presentation; enlarged hyperchromatic cells within fibrous septae



Adipose tissue

Liposarcomas of soft tissue - general


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 11 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Most common soft tissue sarcoma of adults (20%)
● See also discussion in Breast-malignant, Heart-tumor, Liver-tumor, Oral Cavity, Pleura and Testis chapters

Epidemiology
=========================================================================

● Age 40+ years
● Most cases in children are actually lipoblastoma or giant cell fibroblastoma
● Rarely associated with multiple benign lipomas

Sites
=========================================================================

● Deep soft tissue (thigh, retroperitoneum, popliteal fossa)
● Mediastinum is uncommon (Am J Surg Pathol 2007;31:1868)
● Head and neck cases are often initially misdiagnosed, 53% recur (Head Neck 2009;31:28)
● Usually NOT superficial, NOT intramuscular, NOT in neck

Treatment and prognosis
=========================================================================

● Tumor size and histologic classification are important prognostic factors
● Surgery still remains the mainstay of treatment and the only approach offering the potential of cure
● Postoperative radiation reduces recurrence rate
● 10 year local recurrence-free and metastasis-free survival in low-grade group is 87% and 95%, and in high-grade group is 75% and 61% (Cancer 2008;113:1649)

Gross description
=========================================================================

● Large, well circumscribed but not encapsulated
● Mimics myxoma, lipoma and cerebral convolutions

Micro description
=========================================================================

● Per WHO (20020, composed of three subtypes:
  (1) well-differentiated and dedifferentiated liposarcoma (WDLPS/DDLPS)
  (2) myxoid and round cell liposarcoma (MLS and RCL)
  (3) pleomorphic liposarcoma (PLS)
● Lipoblasts are relatively specific, resemble fetal fat cells, and are somewhat smaller than mature adipocytes
● Lipoblasts have round, sharply demarcated cytoplasmic lipid (clear) vacuoles which scallop the nucleus and are smaller than vacuoles of mature adipocytes; spikes of chromatin may project between the vacuoles; may resemble signet ring cells or have central nuclei with small indentations by multiple fat vacuoles

Positive stains
=========================================================================

● S100 (often), calretinin (Hum Pathol 2006;37:312)

Electron microscopy description
=========================================================================

● Lipoblasts resemble brown fat cells; are multivacuolated with lipid droplets, micropinocytotic vesicles, glycogen, external lamina, intermediate filaments, Golgi, rough and smooth endoplasmic reticulum, mitochondria
● Lipoblasts frequently are close to capillaries and pericytes
● Also lipid-free, poorly differentiated mesenchymal cells (Am J Clin Pathol 1986;85:649)

Differential diagnosis
=========================================================================

● Clear cell melanoma: strong S100+, HMB45+
● Fat necrosis: histiocytes are often circumferential around lipid droplets, associated with trauma, have central nucleus which is not deformed
● Infiltration of fat by nonfatty tumors: fat cells are normal size and at periphery of lesion
● Inflammatory lipoma
Intramuscular myxoma
Lipoblastoma / lipoblastomatosis
● Lipogranuloma
● Localized lipoatrophy: insulin injection sites
● Metastatic signet ring cell carcinoma: infiltrative, cytokeratin+, mucin+
Pleomorphic / spindle cell lipoma
● Silicon granuloma (image)

Additional references
=========================================================================

eMedicine #1; #2



Adipose tissue

Atypical lipomatous tumor / well differentiated liposarcoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 12 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Low grade malignancy of relatively mature adipocytes that exhibit focal atypia

Terminology
=========================================================================

● Called atypical lipomatous tumor in periphery
● Use of “atypical lipoma” is not recommended
Suggestion: call “well differentiated liposarcoma” in retroperitoneum or central body site and “atypical lipomatous tumor” elsewhere

Epidemiology
=========================================================================

● Common liposarcoma subtype (40-45% of liposarcomas)
● Adults, peaks at ages 40-60 years
● Very rare in children

Sites
=========================================================================

● Usually lower limbs, retroperitoneum, trunk, head and neck region, also paratesticular, mediastinum or subcutaneous tissue
● Unusual sites include parotid gland, esophagus, mesentry, breast

Case reports
=========================================================================

● 36 year old woman with gluteal mass (World J Surg Oncol 2006;4:33)
● 43 year old woman with abdominal fullness and weight gain (Hinyokika Kiyo 2010;56:697)
● 73 year old man with mesenteric tumor (Case Rep Oncol 2011;4:178)

Treatment and prognosis
=========================================================================

● Excision; negative margins are particularly important for sclerosing subtype (Ann Surg Oncol 2004;11:78)
● Does not metastasize unless it dedifferentiates, which is associated with shorter survival (Am J Surg Pathol 2007;31:1)
● Subcutaneous or intramuscular tumors may recur but typically do not dedifferentiate or metastasize
● Retroperitoneal or central body site tumors are difficult to resect with a clear margin; frequently recur, dedifferentiate and cause death
● Sample carefully to look for dedifferentiated component
● Retroperitoneal / intra-abdominal location is associated with the worse outcome (J Surg Res 2012;175:12)

Clinical images
=========================================================================



Intraoperative thigh mass


Pelvic tumor during surgery

Gross description
=========================================================================

● Circumscribed or infiltrative
● Bulging, large (particularly in retroperitoneum), yellow-white
● Resembles lipoma
● Coarsely lobulated with pale, firm areas
● Fat necrosis in large lesions

Gross images
=========================================================================



Thigh masses


Retroperitoneal tumors


Mesenteric tumor


Pelvic tumor

Other images: tumor of mesocolon

Micro description
=========================================================================

● Mature fat plus variably sized adipocytes and fibromyxoid stroma containing spindle cells with large, deep-staining nuclei and marked nuclear enlargement or pleomorphism
● Cellularity is low and mitotic figures are uncommon
● Usually fibrous tissue septa are present that may contain spindle cells or highly pleomorphic cells
● Some nuclei have sharply outlined vacuoles (Lochkern)
● Rarely heterologous differentiation
● No/few lipoblasts
● Rarely have no/minimal adipocytes except in recurrences
● Some authors do not require any atypia for diagnosis of retroperitoneal tumors
● May be associated with metaplastic bone formation (Hinyokika Kiyo 2010;56:697)
● Rarely has low grade osteosarcomatous component (Am J Surg Pathol 2010;34:1361)

Tumors are subtyped, but this has no clinical significance (Semin Diagn Pathol 2001;18:258)
Inflammatory subtype: rare; lymphoid nodules in cellular stroma with atypical multinucleated cells; may obscure lipocytes (see inflammatory liposarcoma)
Lipoleiomyosarcoma subtype: liposarcoma with leiomyosarcomatous differentiation (see lipoleiomyosarcoma)
Lipoma-like subtype: most common subtype; scattered atypical cells; rare to frequent lipoblasts
Sclerosing subtype: retroperitoneal or paratesticular lesions; collagenous fibrous tissue with scattered adipocytes and atypical multinucleated stromal cells; few lipoblasts
Spindle cell subtype: CD34+ spindle cells in short fascicles, whorls or storiform pattern mixed with well differentiated liposarcoma component with hyperchromatic nuclei but only mild atypia
Mixed subtype: very common

Micro images
=========================================================================





Various images


Well circumscribed tumor


Enlarged, dense irregular nuclei


Atypical cells within fibrous tissue


Bizarre shaped cells


Lochkern cells with sharply outlined nuclear vacuoles


Lipoblasts are multivacuolated with atypical nuclei


Floret cells


Thick collagen fibers


Thin collagen fibers


Moderately cellular (but not dedifferentiated)


Atypical cells within blood vessel walls


Subcutaneous tumor


Metaplastic bone


Metaplastic smooth muscle


Immunostains

Cytology description
=========================================================================

● Large cells with multilobulated nuclei and mature appearing adipocytes
● May have bizarre tumor cells (Acta Cytol 2000;44:459)

Positive stains
=========================================================================

● MDM2 and CDK4 (both together are sensitive and specific, Am J Surg Pathol 2005;29:1340)
● S100 (adipocytes in 2/3 of cases)
● CD34 (some spindle cells)
● Usually p16 (Appl Immunohistochem Mol Morphol 2009;17:51)

Negative stains
=========================================================================

● HMB45

Electron microscopy description
=========================================================================

● Pseudoinclusions due to invaginations of nuclear membrane

Molecular / cytogenetics description
=========================================================================

● Ring or giant marker/rod chromosomes derived from 12q13-15 in almost all cases
● Amplifications of the 12q12-21 and 10p11-14 regions (Virchows Arch 2012;461:67)
● MDM2 and CDK4 by FISH or real time PCR can differentiate from other sarcomas (Hum Pathol 2006;37:1123, Am J Surg Pathol 2007;31:1476)
Carboxypeptidase M amplification may be alternative diagnostic tool (Mod Pathol 2009;22:1541)
● Other rearrangements include amplifications of 12q12-21 and 10p11-14 regions (Virchows Arch 2012;461:67), hypertriploid, #8 rearrangements (Oncol Rep 2005;13:649)

Molecular images
=========================================================================



(A) ring chromosome, (B) giant marker chromosome, (C) anaphase bridge


(A) ring chromosome, (B) giant marker chromosome, (C) anaphase bridge

Differential diagnosis
=========================================================================

Lipoma: no atypical nuclei
Lipomatous angiomyolipoma: HMB45+ epithelioid cells, MDM2 and CDK4 negative (Pathol Int 2006;56:638)
Lipoblastoma: age 3 or younger, MDM2 and CDK4 negative (Virchows Arch 2002;441:299)
Paraffinoma: history of paraffin injection, no atypical nuclei, MDM2 and CDK4 negative (Br J Radiol 2003;76:264)
Malignant fibrous histiocytoma: no adipocytes, MDM2 and CDK4 negative
Retroperitoneal round cell/myxoid liposarcoma: morphology may be similar, but negative for MDM2, CDK4 and 12q13-15 amplification (Mod Pathol 2009;22:223)

Additional references
=========================================================================

Stanford University



Adipose tissue

Inflammatory liposarcoma - subtype of atypical lipomatous tumor / well differentiated liposarcoma


Reviewer: Charanjeet Singh, M.D. (see Reviewerspage)
Revised: 12 November 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Nodular aggregates of chronic inflammatory cells with scattered large atypical cells
● Paucicellular stroma with fibroblastic cells
● Remaining lesion is typical well differentiated liposarcoma (Am J Surg Pathol 1997;21:518)
● Not a WHO diagnosis

Epidemiology
=========================================================================

● Rare variant with similar clinical presentation to classic type (Am J Surg Pathol 1997;21:884)

Case reports
=========================================================================

● 37 year old man with 35 cm abdomino-pelvic mass (Indian J Cancer 2006;43:36)
● 67 year old man with diffuse large B cell lymphoma (Patholog Res Int 2010;2010:505436)
● 79 year old woman with thigh mass (Arch Pathol Lab Med 2004;128:e21)

Gross images
=========================================================================



35 cm tumor weighing 9 kg


Retroperitoneal tumor

Micro description
=========================================================================

● Prominent chronic inflammation that resembles lymphoma and may obscure sarcomatous component
● Lymphocytes distributed in 3 distinct patterns:
  (1) Scattered throughout the tumor, both in fibrous septae and in adipocytic areas
  (2) In clusters; or
  (3) As immature follicles
● Clusters and follicles are usually perivascular; vessels are surrounded by lymphocytes, but with no evidence of vasculitis (Am J Surg Pathol 2012;36:941)

Micro images
=========================================================================



Inflammatory variant


Focal dense inflammatory infiltrate


Various images

Cytology description
=========================================================================

● Numerous dispersed lymphocytes and plasma cells
● Scattered large atypical cells with abundant ill defined cytoplasm, multiple or hyperlobated nuclei and coarse chromatin
● Also fibrous tissue fragments containing both types of cells (Diagn Cytopathol 1999;20:229)

Differential diagnosis
=========================================================================

● Hodgkin’s lymphoma - no well differentiated liposarcoma component, no lipoblasts, negative for MDM2, CDK4, 12q13-15 rearrangement
● Inflammatory pseudotumor - no well differentiated liposarcoma component, no lipoblasts, negative for MDM2, CDK4, 12q13-15 rearrangement (Am J Surg Pathol 1997;21:884)
● MFH-inflammatory - no well differentiated liposarcoma component, no lipoblasts, negative for MDM2, CDK4, 12q13-15 rearrangement
● Sclerosing mesenteritis or idiopathic retroperitoneal fibrosis - no well differentiated liposarcoma component, no lipoblasts, negative for MDM2, CDK4, 12q13-15 rearrangement (Mod Pathol 2009;22:66)



Adipose tissue

Lipoleiomyosarcoma - subtype of atypical lipomatous tumor / well differentiated liposarcoma


Reviewer: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 13 November 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Well-differentiated liposarcoma with a leiomyosarcomatous component
● Not a WHO diagnosis

Epidemiology
=========================================================================

● Rare
● May be a dual lineage sarcoma with multifocal smooth muscle component arising from atypical changes in vessel wall, and separate from atypical changes in fat (Am J Surg Pathol 2002;26:742)

Treatment and prognosis
=========================================================================

● Similar prognosis to conventional well differentiated liposarcoma

Case reports
=========================================================================

● 76 year old man with mediastinal tumor (Pathology 1997;29:428)

Micro description
=========================================================================

● Combined features of liposarcoma and leiomyosarcoma
● Well differentiated tumors are low grade
● May arise from or mix with smooth muscle in walls of large vessels within the tumor

Micro images
=========================================================================



Uterine tumor: H&E and caldesmon

Differential diagnosis
=========================================================================

Dedifferentiated liposarcoma: highly atypical smooth muscle or other types of sarcoma present
Myolipoma: bland smooth muscle present; no lipoblasts, negative for MDM2, CDK4, no 12q13-15 rearrangement
Angiomyolipoma: smooth muscle has cytoplasmic clearing, no fibrous septae or hyperchromatic stromal cells, no lipoblasts; positive for melanoma markers, negative for MDM2, CDK4, no 12q13-15 rearrangement

Additional references
=========================================================================

Int J Gynecol Pathol 2012;31:358 (uterus), Head Neck 2012 Feb 6 [Epub ahead of print] (larynx)



Adipose tissue-liposarcoma

Dedifferentiated liposarcoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 12 November 2014, last major update August 2012
Copyright: (c) 2003-2014, PathologyOutlines.com, Inc.

Definition
=========================================================================

● Well differentiated liposarcoma with abrupt transition to dedifferentiated (high grade or low grade) morphology

Epidemiology
=========================================================================

● Older adults
● Occurs in up to 10% of well differentiated liposarcomas, more often retroperitoneal than superficial tumors
● Dedifferentiated component usually is in recurrent or metastatic foci; possibly in original excision

Sites
=========================================================================

● More common in retroperitoneal lesions or spermatic cord, also in extremity tumors
● Rare in subcutaneous tumors

Case reports
=========================================================================

● 23 year old with orbital tumor (Int J Ophthalmol 2011;4:452)
● 53 year old man with retroperitoneal tumor exhibiting paraganglioma-like pattern (Arch Pathol Lab Med 2004;128:788)
● 62 year old man with 8 cm axillary mass (J Radiol Case Rep 2012;6:9)
● 67 year old woman with retroperitoneal tumor with leiomyosarcomatous differentiation and hCG production (Sarcoma 2008;2008:658090)
● 71 year old whose relapse had extensive lymphoid component (Pathol Res Pract 2005;201:347)
● 71 year old woman with thigh mass exhibiting osteosarcomatous dedifferentiation (Radiographics 2005;25:1082)
● 72 year old man with arm tumor and leukocytosis (World J Surg Oncol 2007;5:131)
● 76 year old woman with abdominal mass (World J Gastrointest Oncol 2011;3:116)
● 85 year old woman with soft tissue mass of buttock (Cytojournal 2010;7:5)
● Three cases with rhabdomyoblastic dedifferentiation (Virchows Arch 2005;447:835)
● Retroperitoneal tumor producing alpha-fetoprotein (Virchows Arch 2006;448:517)

Treatment and prognosis
=========================================================================

● Better prognosis than other high grade pleomorphic sarcomas (Am J Surg Pathol 1994;18:1213), but still recurs in 40-75%, metastasizes in 10-15%, causes death in 30-50% (Am J Surg Pathol 1997;21:271)
● Metastases associated with low or high grade dedifferentiation (have similar behavior), those with myxofibrosarcoma-like features are rapidly fatal (Mod Pathol 2005;18:976)
● Must rule out dedifferentiated liposarcoma in any retroperitoneal sarcoma by (1) adequate sampling, particularly of peripheral areas, (2) cytogenetics, (3) immunostaining for MDM2 and CDK4 or molecular testing for 12q13-15 amplification
● Retroperitoneal dedifferentiated liposarcomas have higher rates of local recurrence and disease specific death rates (Curr Opin Oncol 2011;23:373)

Clinical images
=========================================================================



Intraoperative image of axillary tumor

Gross description
=========================================================================

● Large firm mass (may resemble “fish-flesh”) with coarse lobulation, often surrounded by benign appearing well differentiated component

Gross images
=========================================================================



Various images

Micro description
=========================================================================

● Well differentiated and dedifferentiated components, often with abrupt transition
● Dedifferentiated component is cellular, nonlipogenic sarcoma with 5+ mitotic figures/10 HPF
● Usually high grade, often resembles MFH with short fascicles of spindled and pleomorphic cells
● Heterologous elements in 10%
● Less common is low grade tumor resembling fibromatosis or well differentiated fibrosarcoma
Metastases: usually contain dedifferentiated component only
Variant: neural-like whorling growth pattern and metaplastic bone formation (Cancer Genet Cytogenet 2007;172:147, Histopathology 1998;33:414, Am J Surg Pathol 1998;22:945)

Micro images
=========================================================================



Various images


Fibromatosis-like areas


Fibrosarcoma and solitary fibrous tumor-like patterns


Hemangiopericytoma-type pattern


Leiomyosarcomatous differentiation in retroperitoneal tumor with hCG production


MFH-like areas


Myxofibrosarcoma-like pattern


Neural appearance


Osteosarcomatous differentiation


Paraganglioma-like pattern


Rhabdomyosarcomatous elements


Storiform pattern


Retroperitoneal tumors: various patterns


H&E and MDM2 staining


Left to right: PPAR-gamma, Rb

Cytology description
=========================================================================

● Hypercellular with multinucleated, pleomorphic giant cells with abundant cytoplasm, small clusters of cells with high N/C ratio, spindled cells with elongated nuclei (Acta Cytol 2001;45:641)
● Occasional osteoclast type giant cells (Cytojournal 2010;7:5)

Cytology images
=========================================================================



FNAB of dedifferentiated liposarcoma

Positive stains
=========================================================================

● MDM2 and CDK4 (both together are sensitive and specific, Am J Surg Pathol 2005;29:1340)
● Also vimentin, p53, Rb (66%), PPAR-gamma (Mod Pathol 2008;21:517) focal positive for smooth muscle actin, MIB1 / Ki-67

Molecular / cytogenetics description
=========================================================================

● MDM2+, CDK4+
● 12q14 amplification, often due to supernumerary ring or giant chromosome derived from 12q13-15 region - also found in tumors with whorling growth pattern (Cancer Genet Cytogenet 2007;172:147)

Molecular / cytogenetics images
=========================================================================



Figure 3

Differential diagnosis
=========================================================================

Atypical angiomyolipoma: atypical smooth muscle may resemble sarcoma, but involves kidney, has abnormal blood vessels, HMB45+
Fibrosarcoma: no well differentiated component, no 12q13-15 amplification
Leiomyosarcoma: no well differentiated component, no 12q13-15 amplification
MFH-pleomorphic: retroperitoneal tumors may really be dedifferentiated liposarcomas (Mod Pathol 2003;16:256)
MPNST: no well differentiated component, no 12q13-15 amplification
Pleomorphic liposarcoma: has lipoblasts
Rhabdomyosarcoma: no well differentiated component, no 12q13-15 amplification

Additional references
=========================================================================

Stanford University



Adipose tissue-liposarcoma

Myxoid/round cell liposarcoma - general


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 13 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

See also subtypes myxoid-well differentiated liposarcoma, myxoid-round cell liposarcoma

Epidemiology
=========================================================================

● #2 most common subtype of liposarcoma (33-50% of cases), after well differentiated liposarcoma
● Adults in 20’s to 40’s
● Rare in children under 10 years

Sites
=========================================================================

● Usually limb or thigh in muscle or deep tissue
● Almost never retroperitoneal, only rarely in subcutis
● Either well differentiated/low grade (well differentiated) or poorly differentiated/high grade (round cell)

Treatment and prognosis
=========================================================================

● Wide local excision, possibly radiotherapy (Cancer 2009;115:3254) or chemotherapy to prevent recurrence
● Poor prognostic factors include poorly differentiated (round cell) component, large size, necrosis, high Ki-67 (J Clin Pathol 2003;56:579), p53 overexpression (Clin Cancer Res 2001;7:3977)
● Has both pulmonary and extrapulmonary metastatic deposits; pulmonary metastatic lesions are usually high grade lesions (Sarcoma 2012;2012:345161)
● Patients with >5% round cell component are at higher risk of local recurrence, metastasis and tumor-related death and should be considered for adjuvant radiotherapy and possibly chemotherapy (Sarcoma 2011;2011:538085)

Micro images
=========================================================================



Various percentages of round cells


Comparison of low grade and high grade tumors

Molecular / cytogenetics description
=========================================================================

● Associated with t(12;16)(q13;p11) - FUS-DDIT3 also called TLS-CHOP fusion gene in 90% (J Mol Diagn 2000;2:132)
● Less common is t(12;22)(q13;p11) - EWSR1-DDIT3 (Cancer Res 1995;55:24) or ins(12;16)(q13;p11.2p13) (Am J Clin Pathol 1997;108:35)
● Multifocal tumors may originate from same clone (Clin Cancer Res 2000;6:2788)
● Have immature adipogenic status (Hum Pathol 2009;40:1244)

Additional references
=========================================================================

Atlas of Genetics and Cytogenetics, Stanford University, OMIM 126337 (DDIT3/CHOP)



Adipose tissue-liposarcoma

Well differentiated myxoid liposarcoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 13 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

Definition
=========================================================================

● Low grade tumor with primitive non-lipogenic mesenchymal cells, signet ring lipoblasts and prominent myxoid stroma with branching vascular pattern

Terminology
=========================================================================

● Also called paucicellular myxoid liposarcoma

Epidemiology
=========================================================================

● Peaks in 30’s and 40’s
● May occur in children, very rarely in elderly

Sites
=========================================================================

● Usually thigh and lower extremity of young adults
● Retroperitoneal involvement is rare

Case reports
=========================================================================

● 71 year old man with supraclavicular fossa mass (Chest 2000;117:1518)
● Young men with multicentric tumors (World J Surg Oncol 2007;5:139)

Treatment and prognosis
=========================================================================

● Median survival 105 months (Ann Surg Oncol 2007;14:1507)
● Pure tumors (without round cells) have low grade behavior with only rare metastases
● Poorer prognosis if round or pleomorphic cells

Gross images
=========================================================================





Various images

Other images: well circumscribed white tumor;   lobulated gray-white tumor within skeletal muscle

Micro description
=========================================================================

● Low grade and paucicellular with monomorphic, stellate or fusiform cells without atypia
● Prominent chicken wire vasculature (delicate thin walled arborizing and curving capillaries)
● Numerous signet ring lipoblasts, particularly at periphery of lobules, has mucoid matrix rich in hyaluronidase sensitive acid mucopolysaccharides, may have large mucoid pools
● Lymphangioma-like cystic degeneration is relatively specific
● Rarely metaplastic cartilage or cartilage with TLS-CHOP fusion gene (Appl Immunohistochem Mol Morphol 2007;15:477)
● No/rare mitotic figures

Micro images
=========================================================================



Histological sections of a myxoid liposarcoma showing sheets of multivacuolated lipoblasts with atypical nuclei (blue arrows) and interspersed arborising thin-walled vessels


Large (mature) and small fat cells


Resembles pulmonary edema due to large irregular cystic spaces, some with granular eosinophilic material


Hypocellular zones: left-small artery, middle-veins, right-transition between cellular and hypocellular areas


Cords of cells resembling myxoid chondrosarcoma


Hyalinized collagenous stroma (rare finding)




Lipoblasts, myxoid stroma and branched capillaries


Signet ring lipoblasts

 
Metastases

Other images: lipoblasts, myxoid stroma and branched capillaries #1;   #2;   #3;   lipoblasts #1;   #2;   #3;   #4

Cytology description
=========================================================================

● Myxoid material with arborizing blood vessels and lipoblasts (Acta Cytol 2007;51:456)

Positive stains
=========================================================================

● Vimentin, S100, CD36 (Am J Clin Pathol 1995;103:20)

Electron microscopy description
=========================================================================

● White adipose tissue, aggregates of 60-Angstrom intermediate filaments and large masses of glycogen (Am J Clin Pathol 1979;72:521)
● Cells have investing basal lamina, pinocytotic vesicles, cytoplasmic glycogen and cytoplasmic lipid (Am J Surg Pathol 1980;4:163)
● Resembles lipoblastoma

Differential diagnosis
=========================================================================

Extraskeletal myxoid chondrosarcoma: malignant chondrocytes, no cytoplasmic fat vacuoles, no prominent vasculature
Lipoblastoma: similar histology but age 5 years or less
Myxofibrosarcoma: older adults, often superficial, infiltrative, no cytoplasmic fat vacuoles, more nuclear atypia, thicker curvilinear vessels, frequent mitotic figures
Myxoma: extremely paucicellular, lacks a prominent vascular component



Adipose tissue-liposarcoma

Round cell liposarcoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 14 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● High grade tumor composed of small round or spindled cells with frequent mitotic figures
● Also called poorly differentiated myxoid liposarcoma

Treatment and prognosis
=========================================================================

● Aggressive, poor outcome if at least 5% of tumor is round cell (Am J Surg Pathol 1996;20:171, Cancer 1996;77:1450)
● Frequently metastasizes to retroperitoneum, pleural cavity, soft tissue or pelvis; less often to lung
● Median survival 55 months (Ann Surg Oncol 2007;14:1507)

Case reports
=========================================================================

● 28 year old man with painful subcutaneous mass on flank (Ann Dermatol 2011;23:338)
● 30 year old man with thigh mass (Case of the Week #10)
● 60 year old woman with retroperitoneal mass (University of Pittsburgh)
● Young adult with scrotal swelling (J Med Assoc Thai 2005;88:1302)

Clinical images
=========================================================================



Various images

Gross description
=========================================================================

● Opaque white nodules, fleshy

Gross images
=========================================================================



Thigh tumor post-chemotherapy


44 year old woman with axillary tumor (R-round cell component)

Micro description
=========================================================================

● Cellular areas of small, round or spindled cells with sparse eosinophilic and granular cytoplasm and large nuclei; may resemble lymphoma or other round cell tumors
● Scattered lipoblasts, frequent mitotic figures and necrosis
● Frequent pseudoglandular tumor cells
● Vasculature is less prominent than pure myxoid cases
● Often a transition between well differentiated myxoid and poorly differentiated round cell areas
● Note: classify as round cell if 5% or more of tumor volume

Micro images
=========================================================================



Various images


Sheets of primitive round cells


Small round cells are pleomorphic


Comparison of well differentiated and poorly differentiated (round cell) tumors


Transition between round cell and myxoid areas


Post-chemotherapy

Other images: small round tumor cells with minimal cytoplasm in myxoid stroma,   perivascular pattern,   invasion of fascia,   pseudocystic cavity due to necrosis,   branched capillaries in myxoid poor stroma,   Alcian blue PAS stain

Cytology description
=========================================================================

● Hypercellular smears with single round cells with scant cytoplasm and naked nuclei
● Nuclei usually round, occasionally oval
● Variable background vacuoles, intracytoplasmic vacuoles, fragments of myxoid stroma with neoplastic cells
● No prominent pleomorphism (Cancer 2003;99:28)

Cytology images
=========================================================================


Various images

Positive stains
=========================================================================

● CD31 and CD34 highlight vasculature
● S100+ lipoblasts (30-50%)

Electron microscopy description
=========================================================================

● Lipid vacuoles and massive proliferation of mitochondria (Acta Cytol 1992;36:722)

Molecular description
=========================================================================

● Characteristic t(12;16)(q13:p11) (Am J Surg Pathol 1996;20:1047)
● Activation of the PI3K/Akt pathway via activating mutation of PIK3CA, loss of PTEN, or IGF1R expression have a role in round cell transformation (Mod Pathol 2012;25:212)

Differential diagnosis
=========================================================================

Metastatic carcinoma: clinical history, keratin+ cells, may have more pleomorphism
Melanoma: various histologic patterns, usually prominent nucleoli, S100+ tumor cells, HMB45+
Lymphoma: positive for B (CD20, CD79a) or T cell (CD3, CD4) markers
Ewing’s/PNET: neuroendocrine morphology, CD99+, translocations involving EWS gene



Adipose tissue-liposarcoma

Pleomorphic liposarcoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 21 December 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Widespread high grade, pleomorphic tumor cells with some lipoblasts but no evidence of well differentiated liposarcoma

Epidemiology
=========================================================================

● 5% of all liposarcomas
● No gender preference
● Median age 54-70 years; rare in childhood
● Associated with radiation therapy or neurofibromatosis

Sites
=========================================================================

● Thigh (29%), internal trunk (21%), limb girdles (18%), upper extremity (16%), thoracoabdominal wall (10%)
● Often deep seated or extracompartmental

Case reports
=========================================================================

● 42 year old man with pericardial tumor (Interact CardioVasc Thorac Surg 2010;11:325)
● 47 year old woman with breast mass (Indian J Pathol Microbiol 2011;54:124)
● 70 year old male with pectoral wall mass (J Can Res Ther 2009;5:315)
● 71 year old woman with tumor of foot (Diagn Pathol 2008;3:15)
● 72 year old man with epithelioid tumor (Pathol Res Pract 2004;200:545)
● Post-radiotherapy for epithelioid sarcoma (Pathol Oncol Res 2000;6:287)

Treatment and prognosis
=========================================================================

● Wide local excision or amputation with postoperative radiotherapy (Am J Surg Pathol 2004;28:1257), also chemotherapy
● Aggressive; often recurs locally (40%), metastasizes (40%), causes death (35%)
● 5 year overall survival 60%
● Poor prognostic factors: age 60+, truncal (central) location, deep, size >5 cm, vascular invasion, incomplete excision (Am J Surg Pathol 2002;26:601)

Clinical images
=========================================================================



Pectoral wall mass

Gross description
=========================================================================

● Often large (median 8-10 cm, up to 23 cm), multinodular, white-yellow
● Areas of hemorrhage and necrosis common
● Usually deep (subfascial), often myxoid or necrotic areas

Gross images
=========================================================================



Left to right: retroperitoneum, thigh, upper arm


Infiltrating gluteus muscle


Retroperitoneum

Micro description
=========================================================================

● Well circumscribed but non-encapsulated with infiltrative borders
● At least focal typical liposarcomatous areas
● Pleomorphic cells cover > 65% of cut surface with MFH-like, round cell liposarcoma-like (without vascular network), spindle cell liposarcoma-like or epithelioid cells (Mod Pathol 1999;12:722)
● Usually high grade with enlarged round to bizarre nuclei
● Tumor necrosis common
● Median 25 mitotic figures/10 HPF
● May have neutrophils within giant cells, hemangiopericytic foci, extra- and intracellular hyaline droplets
● Epitheloid variant often confused with carcinoma

Micro images
=========================================================================



Various images


Left: retroperitoneum; right: pectoral wall


Left: some lipoblasts are present; right: vacuolated lipoblasts


Myxoid stroma with markedly pleomorphic cells


Pleomorphic lipoblasts


Pleomorphic round cells


MFH-like areas


Markedly atypical cells


Comparison with pleomorphic rhabdomyosarcoma


Thigh tumor metastatic to thyroid gland


Varying degrees of lipogenic differentiation and signet ring cells

Cytology description
=========================================================================

● Pleomorphic spindle cells of high grade sarcoma with occasional lipoblasts

Positive stains
=========================================================================

● Vimentin, S100 (lipogenic areas in 33%), smooth muscle actin (45%)
● CD34, keratin (21%), desmin (13%)

Electron microscopy description
=========================================================================

● Abundant coalescing lipid droplets, numerous cytoplasmic organelles

Molecular / cytogenetics description
=========================================================================

● Complex karyotype
● Shares similar genomic imbalances with myxofibrosarcoma (Lab Invest 2005;85:176)
● Epithelioid variant rarely has t(12;16)(q13;p11) - TLS-CHOP, more commonly seen in myxoid and round cell liposarcoma (Histopathology 2005;46:334)

Differential diagnosis
=========================================================================

Pleomorphic lipoma: ropy collagen, no/rare mitotic figures
Dedifferentiated liposarcoma: also has well differentiated component
Metastatic carcinoma: keratin+ or other evidence of epithelial differentiation, no liposarcomatous differentiation
MFH-pleomorphic: no definite lipoblasts
Pleomorphic rhabdomyosarcoma: skeletal muscle differentiation

Additional references
=========================================================================

Mod Pathol 2001;14:179, Stanford University



Adipose tissue-liposarcoma

Mixed type liposarcoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 13 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Mixture of myxoid/round cell, well differentiated/dedifferentiated and pleomorphic types

Epidemiology
=========================================================================

● Rare
● Affects elderly patients, usually in retroperitoneum
● Morphologic differences are due to differential expression of multiple genes (Pathology 2006;38:114)

Case reports
=========================================================================

● 11 year old girl with cough, dyspnea and fever due to mediastinal tumor (Indian J Pathol Microbiol 2010;53:525)
● 45 year old woman with thigh tumor (Virchows Arch 2008;453:197)
● 50 year old man with retroperitoneal tumor (Am Surg 2008;74:1202)
● 52 year old man with intramuscular tumor in thigh and 62 year old man with intramuscular tumor in calf (Jpn J Clin Oncol 2003;33:482)
● 62 year old man with axillary mass (J Radiol Case Rep 2012;6:9)
● 75 year old man with scrotal swelling (Romanian Journal of Morphology and Embryology 2008;49:105)

Gross description
=========================================================================

● Large multinodular masses
● Cystic/solid
● Gray-white-yellow

Gross images
=========================================================================



Thigh tumor


Calf tumor

Micro images
=========================================================================



Tumors (left to right) of calf, mediastinum, thigh



Adipose tissue-liposarcoma

Sclerosing poorly differentiated liposarcoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 13 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
=========================================================================

● Dense stromal sclerosing tumor with scattered atypical pleomorphic cells with lipoblastic features
● Not a WHO diagnosis

Epidemiology
=========================================================================

● Single study to date (Histopathology 2008;52:283)
● Mean age 63 years, range 39-90 years, no gender preference
● Either de novo or recurrence of previously resected liposarcoma
● May represent a morphological variant of poorly differentiated liposarcoma
● May be end stage pathway for various liposarcomas
● Aggressive behavior

Micro description
=========================================================================

● Dense stromal sclerosis with scattered atypical pleomorphic cells with lipoblastic features

Molecular/cytogenetics description
=========================================================================

● MDM2 amplification in 4 of 7 cases, negative for CHOP translocation



Extraskeletal bone tumors
Extraskeletal aneurysmal bone cyst

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 10 March 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
=========================================================================
Case reports
=========================================================================
Gross description
=========================================================================
Gross images
=========================================================================
Shoulder
Micro description
=========================================================================
Micro images
=========================================================================
Shoulder
Molecular / cytogenetics description
=========================================================================
Differential diagnosis
=========================================================================


Extraskeletal bone tumors
Extraskeletal chondroma

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 1 March 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
=========================================================================
Case reports
=========================================================================
Clinical images
=========================================================================
Thumb tumor
Foot tumor
Gross description
=========================================================================
Gross images
=========================================================================
Foot tumor
Micro description
=========================================================================
Micro images
=========================================================================
Foot tumor
Cytology images
=========================================================================
Foot tumor
Differential diagnosis
=========================================================================


Extraskeletal bone tumors
Extraskeletal chondrosarcoma

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 10 March 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

See subtypes below: embryonal, mesenchymal, myxoid

General
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Gross images
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Thigh tumor
Fallopian tube tumor
Micro description
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Micro images
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Fallopian tube tumor
Positive stains
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Negative stains
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Electron microscopy description
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Molecular / cytogenetics description
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Variants
Embryonal chondrosarcoma
General
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Mesenchymal chondrosarcoma
General
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Case reports
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Clinical images
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Mandible tumor
Primary orbital tumor
Gross images
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Kidney tumor
Micro description
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Micro images
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Renal tumor
Ureteric tumor
Abdominal mass
Primary orbital tumor
Pleural tumor
Mandible tumor
Positive stains
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Molecular / cytogenetics description
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Molecular / cytogenetics images
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G-banded karyotype #1
#2
SKY karyotype


Myxoid chondrosarcoma
General
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Prognostic factors
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Case reports
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Gross description
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Gross images
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Fallopian tube nodule
Thigh tumor
Micro descripton
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Micro images
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Thigh tumor
Uterine adnexa
Various images
Asymptomatic lung mass with severe anemia
Cytology images
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Thigh tumor
Positive stains
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Negative stains
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Molecular / cytogenetics description
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Extraskeletal bone tumors
Extraskeletal chordoma

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 10 March 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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Positive stains
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Extraskeletal bone tumors
Extraskeletal Ewing sarcoma / PNET

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 10 March 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
=========================================================================
Case reports
=========================================================================
Gross images
=========================================================================
Knee
Micro description
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Micro images
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Inguinal mass
Various images
Positive stains
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Negative stains
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Electron microscopy description
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Molecular / cytogenetics description
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Molecular / cytogenetics images
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t(4;22)(q31;q12)
Differential diagnosis
=========================================================================


Extraskeletal bone tumors
Extraskeletal osteosarcoma

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 10 March 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
=========================================================================
Case reports
=========================================================================
Clinical images
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Skin of lower abdomen
Gross images
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Retroperitoneal mass
Upper arm mass
Micro description
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Micro images
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Upper arm
Chest wall
Retroperitoneal mass
Cutaneous tumor on scar of previous bone graft
Differential diagnosis
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Extraskeletal bone tumors
Parachordoma

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 10 March 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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Case reports
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Micro description
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Micro images
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Presacral tumor
Upper arm
Shoulder mass
Positive stains
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Negative stains
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Molecular / cytogenetics description
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Differential diagnosis
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End of Soft Tissue > Superpage 1


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