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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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Stanford University

 

End of Soft Tissue Tumors > Dedifferentiated liposarcoma

 

 

 

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