[121] The Prevalence of FUS Rearrangement in Sclerosing Epithelioid Fibrosarcoma

W-L Wang, HL Evans, JM Meis, D Lopez-Terrada, AJ Lazar. The University of Texas M.D. Anderson Cancer Center, Houston, TX; Baylor College of Medicine/Texas Children's Hospital, Houston, TX

Background: Several recent reports have described low grade fibromyxoid sarcoma (LGFMS) with sclerosing epithelioid fibrosarcoma (SEF)-like areas. We recently encountered 3 such cases harboring the re-arrangement of FUS (16p11) characteristic of LGFMS detected by fluorescence in-situ hybridization (FISH). Since the established morphologic spectrum of LGFMS includes cases with an identical reciprocal chromosomal translocation previously described as "hyalinizing spindle cell tumor with giant rosettes", we evaluated classic cases of pure SEF for FUS rearrangement to determine whether this entity could be related to LGFMS as well.
Design: Available FFPE tissue from 3 genetically confirmed LGFMS with SEF-like areas and 16 classic SEF (without LGFMS areas) were retrieved from the pathology files of our institution and tabulated with clinical information. Unstained slides from FFPE blocks were prepared and FISH was performed using a commercial FUS break-apart probe.
Results: For the 16 SEF cases, the median age at presentation was 46 (14-78) years with equal gender ratio. SEF most commonly involved the abdomen/retroperitoneum (n=4) and lower extremities (n=4). Only 1 of 16 pure SEF cases showed rearrangement in the FUS locus. The 3 cases of LGFMS with SEF-like areas had FUS rearrangement in both the LGFMS and SEF-like areas documented by FISH.
Conclusions: Only 1 of 16 classic SEF contained a rearrangement of FUS (16p11) detected by FISH. Although cytogenetically-confirmed LGFMS can have SEF-like areas, FUS rearrangement appears to be rare in classic, pure SEF. Since FUS rearrangement is so characteristic of LGFMS, it seems likely that LGFMS with SEF-like areas and SEF share morphologic overlap, but SEF lacks the recurrent molecular determinate of LGFMS.
Category: Bone & Soft Tissue

Monday, March 22, 2010 11:15 AM

Platform Session: Section F, Monday Morning


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