Soft Tissue Tumors - Dedifferentiated liposarcoma

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Soft Tissue Tumors

Adipose tissue-liposarcoma

Dedifferentiated 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.

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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● 23 year old with orbital tumor (Int J Ophthalmol 2011;4:452)
● 53 year old man with retroperitoneal tumor exhibiting paraganglioma-like pattern (Arch Pathol Lab Med 2004;128:788)
● 62 year old man with 8 cm axillary mass (J Radiol Case Rep 2012;6:9)
● 67 year old woman with retroperitoneal tumor with leiomyosarcomatous differentiation and hCG production (Sarcoma 2008;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)
● 76 year old woman with abdominal mass (World J Gastrointest Oncol 2011;3:116)
● 85 year old woman with soft tissue mass of buttock (Cytojournal 2010;7:5)
● 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 (Am J Surg Pathol 1994;18:1213), but still recurs in 40-75%, metastasizes in 10-15%, causes death in 30-50% (Am J Surg Pathol 1997;21:271)
● Metastases associated with low or high grade dedifferentiation (have similar behavior), those with myxofibrosarcoma-like features are rapidly fatal (Mod Pathol 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
● Retroperitoneal dedifferentiated liposarcomas have higher rates of local recurrence and disease specific death rates (Curr Opin Oncol 2011;23:373)

Clinical images
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Intraoperative image of axillary tumor

Gross description
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● Large firm mass (may resemble “fish-flesh”) with coarse lobulation, often surrounded by benign appearing well differentiated component

Gross images
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Various images

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 contain dedifferentiated component only
● Variant: neural-like whorling growth pattern and metaplastic bone formation (Cancer Genet Cytogenet 2007;172:147, Histopathology 1998;33:414, Am J Surg Pathol 1998;22:945)

Micro images
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Various images

Fibromatosis-like areas

Fibrosarcoma and solitary fibrous tumor-like patterns

Hemangiopericytoma-type pattern

Leiomyosarcomatous differentiation in retroperitoneal tumor with hCG production

MFH-like areas

Myxofibrosarcoma-like pattern

Neural appearance

Osteosarcomatous differentiation

Paraganglioma-like pattern

Rhabdomyosarcomatous elements

Storiform pattern

Retroperitoneal tumors: various patterns

H&E and MDM2 staining

Left to right: PPAR-gamma, Rb

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)
● Occasional osteoclast type giant cells (Cytojournal 2010;7:5)

Cytology images
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FNAB of dedifferentiated liposarcoma

Positive stains
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● MDM2 and CDK4 (both together are sensitive and specific, Am J Surg Pathol 2005;29:1340)
● Also vimentin, p53, Rb (66%), PPAR-gamma (Mod Pathol 2008;21:517) focal positive for smooth muscle actin, MIB1 / Ki-67

Molecular / cytogenetics description
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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)

Molecular / cytogenetics images
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Figure 3

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
● MFH-pleomorphic: retroperitoneal tumors may really be dedifferentiated liposarcomas (Mod Pathol 2003;16:256)
● MPNST: no well differentiated component, no 12q13-15 amplification
● 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 > Adipose tissue-liposarcoma > Dedifferentiated liposarcoma

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