Soft tissue

Adipose tissue tumors

Liposarcoma

Pleomorphic liposarcoma


Editorial Board Member: Farres Obeidin, M.D.
Deputy Editor-in-Chief: Borislav A. Alexiev, M.D.
Stacy D. Webb, M.D.
David Suster, M.D.

Last author update: 11 May 2022
Last staff update: 11 May 2022

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PubMed Search: Pleomorphic liposarcoma pathology

Stacy D. Webb, M.D.
David Suster, M.D.
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Cite this page: Webb SD, Suster D. Pleomorphic liposarcoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueadiposepleomorphiclipo.html. Accessed July 3rd, 2022.
Definition / general
  • Pleomorphic, high grade sarcoma with variable numbers of pleomorphic lipoblasts, without areas that resemble atypical lipomatous tumor / well differentiated liposarcoma (or other lines of differentiation) and absence of MDM2 gene alterations by cytogenetic and molecular studies
Essential features
  • Pleomorphic spindle / epithelioid cell sarcoma with variable number of pleomorphic lipoblasts
ICD coding
  • ICD-O: 8854/3 - pleomorphic liposarcoma
  • ICD-11: 2B59.Y & XH25R1 - liposarcoma, other specified primary site & pleomorphic liposarcoma
Epidemiology
Sites
Etiology
  • Unknown
Clinical features
  • Rapidly growing, painless mass
  • Some report pain or other symptoms related to tumor location
Diagnosis
  • Requires histological examination on core needle biopsy or excision
Laboratory
  • No specific laboratory abnormality is known
Radiology description
  • Soft tissue mass with heterogeneous areas of necrosis and hemorrhage, containing less / no fatty tissue (Radiographics 2005;25:1371)
Radiology images

Images hosted on other servers:

MRI of breast mass

CT heterogeneously enhanced mass

Prognostic factors
  • Aggressive, often exhibiting local recurrence and metastatic rates of 30 - 50%
  • 5 year overall survival of ~60%
  • Most common site of metastasis are lungs; however, may occur in various other organs, including pleura, liver and bone
  • Poor prognostic factors: central location, increased tumor depth, greater size and higher mitotic count (Am J Surg Pathol 2002;26:601, Am J Surg Pathol 2004;28:1257)
Case reports
Treatment
Gross description
  • White-yellow, relatively firm, often large (median 8 - 10 cm), multinodular tumors
  • Tumors are usually well demarcated but not encapsulated
  • Often demonstrate myxoid changes with foci of necrosis and hemorrhage
  • Can show foci or scattered areas of cystic degeneration (Mod Pathol 2001;14:179)
Gross images

Contributed by David Suster, M.D.

Well circumscribed tumor mass

Frozen section description
  • Diagnosis typically not made on frozen section; however, generally a diagnosis of high grade sarcoma may be rendered based on degree of cytologic atypia, mitotic activity and whether necrosis is present
Microscopic (histologic) description
  • Varying proportion of pleomorphic lipoblasts in a background of a high grade, usually pleomorphic, undifferentiated sarcoma (Surg Pathol Clin 2019;12:63, Histopathology 2014;64:38)
  • Well circumscribed but nonencapsulated with infiltrative borders
  • May display significant morphologic overlap with myxofibrosarcoma, undifferentiated pleomorphic sarcoma and high grade dedifferentiated liposarcoma
  • Cytologically, tumors are composed of high grade cells with varying numbers of pleomorphic and often bizarre, multinucleated tumor cells
    • These tumor cells will often show subtle to prominent cytoplasmic vacuolization with some forms appearing as classic lipoblasts with scalloped nuclei
    • Signet ring lipoblasts may also be scattered throughout tumor in association with malignant cells
  • Epithelioid morphology is seen in about 25% of cases
  • Tumor necrosis common
  • Median 25 mitotic figures/10 high power fields
  • May have neutrophils within giant cells (emperipolesis-like finding), extra and intracellular eosinophilic hyaline droplets (not specific)
Microscopic (histologic) images

Contributed by David Suster, M.D.

Sheets of atypical cells

Extensive necrosis

Bizarre cell shapes

Pleomorphic lipoblast

Bone metastasis


Pleomorphic lipoblasts

Epithelioid morphology

S100 positivity

Negative MDM2

Virtual slides

Images hosted on other servers:

Epithelioid,
hemangiopericytic
pleomorphic
liposarcoma

High grade pleomorphic liposarcoma

Treated pleomorphic liposarcoma

Cytology description
  • Pleomorphic spindle cells of high grade sarcoma with occasional lipoblasts
Positive stains
Electron microscopy description
  • Abundant coalescing lipid droplets, numerous cytoplasmic organelles
Electron microscopy images

Images hosted on other servers:

Lipid vacuoles

Ultrastructure

Molecular / cytogenetics description
Molecular / cytogenetics images

Contributed by Bei You, Ph.D.

Complex karyotype

Videos

Pleomorphic liposarcoma: 5 minute pathology pearls

Pleomorphic liposarcoma (epithelioid variant)

Sample pathology report
  • Thigh, left mass, wide resection:
    • Pleomorphic liposarcoma (19 x 12 x 13 cm), high grade (see synoptic report)
    • Tumor necrosis is present, ~30%
    • No lymphovascular or perineural invasion seen
    • Margins of resection, no tumor seen
    • Pathologic stage: pT3 N0 (no lymph nodes submitted or found)
Differential diagnosis
  • Dedifferentiated liposarcoma:
    • May show a high grade component with pleomorphic features
    • Defined by amplification of 12q13-15 region (MDM2 / CDK4 genes) and will sometimes show an adjacent well differentiated component
  • Metastatic carcinoma:
    • May grow as sheets of poorly differentiated pleomorphic cells
    • Usually lacks adipocytic differentiation and stains positive with cytokeratins
  • Undifferentiated pleomorphic sarcoma and other high grade pleomorphic sarcomas:
    • May show prominent tumor cell pleomorphism but lacks evidence of adipocytic differentiation / lipoblastic cells
  • Pleomorphic lipoma / spindle cell lipoma:
    • May show scattered pleomorphic cells; however, degree of pleomorphism is significantly less than in pleomorphic liposarcoma
    • No overt features of malignancy, such as necrosis, high mitotic activity
    • Characterized by loss of RB1
  • Pleomorphic rhabdomyosarcoma:
    • High grade sarcoma with prominent pleomorphism that may resemble areas of pleomorphic liposarcoma
    • However, usually shows evidence of rhabdomyoblastic differentiation rather than adipocytic differentiation
    • Positive for myogenic markers, such as MyoD1, myogenin and desmin
Board review style question #1

A 77 year old woman presents with a 19 cm deep soft tissue mass in the left lower extremity. A core needle biopsy shows the high grade sarcoma shown in the image above. Which is the most likely diagnosis?

  1. Dedifferentiated liposarcoma
  2. Pleomorphic liposarcoma
  3. Pleomorphic rhabdomyosarcoma
  4. Undifferentiated pleomorphic sarcoma
  5. Well differentiated liposarcoma
Board review style answer #1
B. Pleomorphic liposarcoma. The image shows a high grade sarcoma with bizarre pleomorphic tumor cells that show evidence of adipocytic differentiation in the form of cytoplasmic vacuolization.

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Reference: Pleomorphic liposarcoma
Board review style question #2
What is pleomorphic liposarcoma molecularly characterized by?

  1. Amplification of 12q13-15
  2. Amplification of MDM2 and CDK4
  3. Complex cytogenetic abnormalities without specific, recurrent molecular alterations
  4. Deletions of SMARCB1 gene and loss of INI1 expression
  5. Gene fusion between FUS and DDIT3
Board review style answer #2
C. Complex cytogenetic abnormalities without specific, recurrent molecular alterations. Pleomorphic sarcoma is a high grade sarcoma characterized by complex molecular alterations. The tumors show complex karyotypes with numerous cytogenetic abnormalities. Specific, recurrent alterations have not been identified. The tumors are negative for amplification of MDM2 / CDK4 (12q-13-15 region).

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Reference: Pleomorphic liposarcoma
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