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Soft Tissue Tumors
Dedifferentiated liposarcoma
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Reviewer: David Lucas, M.D., University of Michigan Health Systems (January 2009)
Revised: 22 October 2009, last major update June 2009
Definition
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● Well differentiated liposarcoma with abrupt transition to dedifferentiated (high grade or low grade) morphology
Epidemiology
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● 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
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● More common in retroperitoneal lesions or spermatic cord, also in extremity tumors
● Rare in subcutaneous tumors
Case reports
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● 53 year old man with retroperitoneal tumor exhibiting paraganglioma-like pattern (Archives 2004;128:788)
● 67 year old woman with renal tumor with leiomyosarcomatous differentiation and hCG production (Sarcoma 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)
● Three cases with rhabdomyoblastic dedifferentiation (Virchows Arch 2005;447:835)
● Retroperitoneal tumor producing alpha-fetoprotein (Virchows Arch 2006;448:517)
Treatment and prognosis
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● Better prognosis than other high grade pleomorphic sarcomas (AJSP 1994;18:1213), but still recurs in 40-75%, metastasizes in 10-15%, causes death in 30-50% (AJSP 1997;21:271)
● Metastases associated with low or high grade dedifferentiation (have similar behavior), those with myxofibrosarcoma-like features are rapidly fatal (Mod Path 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
Gross description
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● Large mass, firm (may resemble “fish-flesh”) with coarse lobulation, often surrounded by benign appearing well differentiated component
Gross images
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Osteosarcomatous Retroperitoneal tumor
differentiation
Other images: infiltrating skeletal muscle
Micro description
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● 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 contains dedifferentiated component only
● Variant: neural-like whorling growth pattern and metaplastic bone formation (Cancer Genet Cytogenet 2007;172:147, Histopathology 1998;33:414, AJSP 1998;22:945)
Micro images
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Well differentiated components
Transition between well differentiated and dedifferentiated components
Classic lipoblasts
Chondrosarcoma- and Osteoid Osteosarcoma-like
osteosarcoma-like patterns pattern
Fibromatosis-like areas
Fibrosarcoma and solitary fibrous tumor-like patterns
Hemangiopericytoma-type pattern
Leiomyosarcomatous differentiation
MFH-like areas
Myxofibrosarcoma-like pattern
Neural appearance
Paraganglioma-like pattern
Pleomorphic MFH-like areas
Rhabdomyosarcomatous elements Desmin+
Storiform pattern
Various images
H&E and MDM2 staining MDM2+
PPAR-gamma retinoblastoma gene product
Virtual slide: rhabdomyosarcomatous elements (Virtual slide)
Cytology description
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● 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)
Positive stains
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● MDM2 and CDK4 (both together are sensitive and specific, AJSP 2005;29:1340)
● Also vimentin, p53, Rb (66%), PPAR-gamma (Mod Path 2008;21:517)
Molecular / cytogenetics
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● 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)
Differential diagnosis
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● 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
● MPNST - no well differentiated component, no 12q13-15 amplification
● Pleomorphic MFH - retroperitoneal tumors may really be dedifferentiated liposarcomas (Mod Path 2003;16:256)
● Pleomorphic liposarcoma (has lipoblasts)
● Rhabdomyosarcoma - no well differentiated component, no 12q13-15 amplification
Additional references
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End of Soft Tissue Tumors > Dedifferentiated liposarcoma
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