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Soft Tissue Tumors

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
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● Widespread high grade, pleomorphic tumor cells with some lipoblasts but no evidence of well differentiated liposarcoma

Epidemiology
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● 5% of all liposarcomas
● No gender preference
● Median age 54-70 years; rare in childhood
● Associated with radiation therapy or neurofibromatosis

Sites
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● Thigh (29%), internal trunk (21%), limb girdles (18%), upper extremity (16%), thoracoabdominal wall (10%)
● Often deep seated or extracompartmental

Case reports
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● 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
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● 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
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Pectoral wall mass

Gross description
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● 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
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Left to right: retroperitoneum, thigh, upper arm


Infiltrating gluteus muscle


Retroperitoneum

Micro description
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● 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
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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
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● Pleomorphic spindle cells of high grade sarcoma with occasional lipoblasts

Positive stains
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● Vimentin, S100 (lipogenic areas in 33%), smooth muscle actin (45%)
● CD34, keratin (21%), desmin (13%)

Electron microscopy description
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● Abundant coalescing lipid droplets, numerous cytoplasmic organelles

Molecular / cytogenetics description
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● 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
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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
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Mod Pathol 2001;14:179, Stanford University

End of Soft Tissue Tumors > Adipose tissue-liposarcoma > Pleomorphic liposarcoma


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