Soft tissue

Adipose tissue tumors

Lipoma and variants

Chondroid lipoma



Last author update: 27 April 2022
Last staff update: 27 April 2022

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PubMed Search: Chondroid lipoma

Ummiya Tahir, M.B.B.S.
Nasir Ud Din, M.B.B.S.
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Cite this page: Tahir U, Qureshi MB, Ud Din N. Chondroid lipoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueadiposechondroid.html. Accessed August 14th, 2022.
Definition / general
  • Benign adipose tissue tumor composed of lipoblasts intermixed with mature adipocytes in a myxohyaline chondroid matrix (Ann Diagn Pathol 2012;16:230)
Essential features
  • Rare variant of lipoma with features of immature fat and immature cartilage
  • Rare, slow going, painless mass in adult women
  • Lobulated, circumscribed, deep seated tumor
  • Mostly affects the proximal extremities and limb girdles of adult women
  • Nests and cords of uni and multivacuolated lipoblasts with variable adipose tissue in a myxochondroid matrix
  • Characterized by t(11;16)(q13;p13) translocation (Histopathology 2013;62:925)
  • Surgical excision is curative with rare recurrence
Terminology
  • Extraskeletal chondroma with lipoblast-like cells (first described terminology, subsequently disapproved) (Hum Pathol 1986;17:1285)
ICD coding
Epidemiology
Sites
  • Most common sites: proximal extremities and limb girdles
  • Less common sites: trunk, distal extremities, head and neck (J Clin Diagn Res 2017;11:ED17)
  • Deep seated tumor involves skeletal muscles, deep fibrous connective tissue or deep subcutaneous fat
  • Superficial in 20% of cases
Pathophysiology
  • Shows recurrent t(11;16)(q13;p13) translocation with resultant C11orf95 and MRTFB fusion (Genes Chromosomes Cancer 2010;49:810)
  • Megakaryoblastic leukemia 2 (MKL2) / myocardin related transcription factor B (MRTFB) acts as coactivator of transcription factor serum response factor (SRF)
  • SRF controls cellular processes including cytoskeleton organization, cell migration, growth and differentiation
  • C11orf95 encodes protein of unknown function
Etiology
  • Not known
Clinical features
  • Benign, painless, slow growing tumor of variable duration
  • History of recent increase in size in 50% of cases
  • Reference: Exp Ther Med 2021;22:1087
Diagnosis
  • Requires presence of classic histologic features (i.e., presence of lipoblasts, chondroid cells and adipocytes in a myxohyaline matrix in a circumscribed lobulated tumor)
  • Diagnosis can also be made on cytology (Am J Surg Pathol 1999;23:1300)
Radiology description
  • CT typically shows a well defined, heterogeneously enhancing mass with variable areas of fat attenuation
  • Can exhibit calcification and ossification on radiographs (Australas Med J 2012;5:355, Skeletal Radiol 2004;33:670)
  • MRI usually shows a well defined mass with lobulated areas of T2 hyperintense or fluid-like signal intensity (Balkan Med J 2015;32:107, Skeletal Radiol 1996;25:592)
  • Appears isointense or hypointense to muscle, with focal hyperintense areas (fat areas) on T1 weighted MR images
  • May show hypermetabolic activity at PET / CT
Radiology images

Contributed by Nasir Ud Din, M.B.B.S.
Right upper limb, coronal view

Right upper limb, coronal view

Right upper limb, T1

Right upper limb, T1

Prognostic factors
  • Does not recur or metastasize if completely excised
  • Rare local recurrence
Case reports
Treatment
Gross description
  • Well delineated, frequently encapsulated
  • Multilobulated (33%)
  • Cut surface: yellowish tan, gelatinous
  • Hemorrhagic foci can be seen
  • 1.5 - 11 cm, hemorrhage is associated with size increase
  • Reference: Medicine (Baltimore) 2019;98:e15587
Gross images

Contributed by Nasir Ud Din, M.B.B.S.
Cut surface

Cut surface

Gelatinous appearance

Gelatinous appearance

Microscopic (histologic) description
  • Encapsulated with occasional lobulations
  • Lobulations are formed by fibrous septa
  • Composed of 3 components arranged in nests, cords and sheets in variable proportion:
    • Mature adipose tissue
    • Cells displaying lipoblastic differentiation
    • Myxohyaline chondroid matrix
  • Mature adipocytes contain eccentrically placed nuclei and vacuolated cytoplasm
  • Cells with lipoblastic differentiation may show various patterns:
    • Undifferentiated bland cells with minimal cytoplasm
    • Small univacuolated to multivacuolated lipoblasts with fat droplets scalloping bland nuclei
  • Cells with granular eosinophilic cytoplasm may be seen
  • Rich vascular network: thick walled blood vessels alternate with large, gaping thin walled vascular spaces
  • No significant nuclear atypia or mitotic activity
  • Hemorrhage and hemosiderin deposition can be present (Hum Pathol 1995;26:706)
  • Fibrosis, calcification and metaplastic bone formation may be seen (Skeletal Radiol 2008;37:475)
Microscopic (histologic) images

Contributed by Nasir Ud Din, M.B.B.S.
Lobulated appearance

Lobulated appearance

Cellular morphology

Cellular morphology

Prominent matrix

Prominent matrix

Multivacuolated lipoblasts

Multivacuolated lipoblasts

Cytology description
Cytology images

Images hosted on other servers:
Cell block section

Cell block sections

Positive stains
  • Immunostains are not very helpful in differential diagnosis
  • S100:
    • Positive in mature adipocytes (strong)
    • Lipoblasts (weak)
    • Negative in cells that do not show lipoblastic differentiation
  • Keratins: rarely positive
  • Cyclin D1: positive (Sarcoma 2011;2011:638403)
  • PAS special stain highlights intracytoplasmic glycogen
  • Toluidine and Alcian blue special stains highlight chondroitin sulfate in matrix at low pH
Negative stains
Electron microscopy description
  • Mature adipose tissue (Am J Surg Pathol 1995;19:1272)
  • Small embryonal cells with characteristics of lipoblasts, chondroblasts or both
  • Matrix shows thin filament network, thin collagen fibers and copious proteoglycan particles
Molecular / cytogenetics description
  • Chromosomal translocation t(11;16)(q13;p12-13) (C11orf95-MKL2) (Histopathology 2013;62:925)
  • Rare 3 way translocation involving chromosomes 1, 2 and 5
Molecular / cytogenetics images

Images hosted on other servers:
11;16 translocation

t(11;16) translocation

Videos

Chondroid lipoma pathology

Sample pathology report
  • Brachialis muscle lump, excision:
    • Chondroid lipoma (see comment)
    • Comment: Chondroid lipoma is a rare variant of lipoma characterized by admixture of chondroid cells, lipoblasts and adipocytes in a myxohyaline matrix. The tumor is benign and excision is curative.
Differential diagnosis
  • Soft tissue chondroma:
    • Occurs in hands and feet
    • True hyaline cartilage is present
    • Lacks adipocytic component
  • Atypical lipomatous tumor:
    • Adipocytes in sheets with variation in size and shape
    • Thick fibrous septa that have atypical stromal cells
    • May exhibit myxoid stroma
    • May show metaplastic cartilage
    • MDM2 amplification present
  • Myxoid liposarcoma:
    • Spindle to stellate cells with myxoid stroma
    • Plexiform vasculature
    • Lipoblasts of signet type are typically present
    • Round cell component shows uniform round cells with moderate pleomorphism and scant cytoplasm
    • t(12;16), t(12;22) translocation
  • Extraskeletal myxoid chondrosarcoma:
    • Larger infiltrative mass
    • More lobulated architecture
    • Anastomosing and reticular pattern of uniform spindle to epithelioid cells
    • Prominent myxoid stroma
    • Lacks adipocytes and lipoblasts
    • Characteristic translocation t(9;17), t(9;22)
  • Myoepithelioma of soft tissue:
    • Cells can be round, spindle or plasmacytoid
    • May show myxoid background and chondroid metaplasia
    • Lipoblasts are absent
    • Immunohistochemistry required for diagnosis: cytokeratin, EMA and S100 positive
    • Variable expression of SMA, calponin, p63, GFAP, desmin
  • Chondrolipoma:
    • Typical lipoma with mature hyaline cartilage
Additional references
Board review style question #1

A 30 year old woman presented with a painless lump in right thigh. Excision specimen showed an encapsulated lesion of 4 x 4 cm. Histology showed a circumscribed adipocytic lesion composed of admixture of chondroid cells with vacuolated to eosinophilic cytoplasm, multivacuolated lipoblasts and mature adipocytes in a chondromyxoid background. Mature hyaline cartilage, necrosis and atypia were absent. Occasional mitotic figures were present. What is the most likely diagnosis?

  1. Chondroid lipoma
  2. Chondrolipoma
  3. Extraskeletal myxoid chondrosarcoma
  4. Myxoid liposarcoma
  5. Well differentiated liposarcoma
Board review style answer #1
A. Chondroid lipoma

Comment Here

Reference: Chondroid lipoma
Board review style question #2
Which of the following lipomas shows the presence of lipoblasts?

  1. Angiolipoma
  2. Chondroid lipoma
  3. Chondrolipoma
  4. Myelolipoma
  5. Osteolipoma
Board review style answer #2
B. Chondroid lipoma

Comment Here

Reference: Chondroid lipoma
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