Soft Tissue Tumor - Myxoid/round cell liposarcoma

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Soft Tissue Tumors

Adipose tissue-liposarcoma

Myxoid/round cell liposarcoma - general

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 13 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

See also subtypes myxoid-well differentiated liposarcoma, myxoid-round cell liposarcoma

Epidemiology
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● #2 most common subtype of liposarcoma (33-50% of cases), after well differentiated liposarcoma
● Adults in 20’s to 40’s
● Rare in children under 10 years

Sites
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● Usually limb or thigh in muscle or deep tissue
● Almost never retroperitoneal, only rarely in subcutis
● Either well differentiated/low grade (well differentiated) or poorly differentiated/high grade (round cell)

Treatment and prognosis
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● Wide local excision, possibly radiotherapy (Cancer 2009;115:3254) or chemotherapy to prevent recurrence
● Poor prognostic factors include poorly differentiated (round cell) component, large size, necrosis, high Ki-67 (J Clin Pathol 2003;56:579), p53 overexpression (Clin Cancer Res 2001;7:3977)
● Has both pulmonary and extrapulmonary metastatic deposits; pulmonary metastatic lesions are usually high grade lesions (Sarcoma 2012;2012:345161)
● Patients with >5% round cell component are at higher risk of local recurrence, metastasis and tumor-related death and should be considered for adjuvant radiotherapy and possibly chemotherapy (Sarcoma 2011;2011:538085)

Micro images
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Various percentages of round cells

Comparison of low grade and high grade tumors

Molecular / cytogenetics description
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● Associated with t(12;16)(q13;p11) - FUS-DDIT3 also called TLS-CHOP fusion gene in 90% (J Mol Diagn 2000;2:132)
● Less common is t(12;22)(q13;p11) - EWSR1-DDIT3 (Cancer Res 1995;55:24) or ins(12;16)(q13;p11.2p13) (Am J Clin Pathol 1997;108:35)
● Multifocal tumors may originate from same clone (Clin Cancer Res 2000;6:2788)
● Have immature adipogenic status (Hum Pathol 2009;40:1244)

Additional references
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● Atlas of Genetics and Cytogenetics, Stanford University, OMIM 126337 (DDIT3/CHOP)

End of Soft Tissue Tumors > Adipose tissue-liposarcoma > Myxoid/round cell liposarcoma - general

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