[44] Histologic Spectrum of Myxoid Liposarcoma: Potential Diagnostic Pitfalls on Core Needle Biopsy.

Karen J Fritchie, John R Goldblum, Raymond R Tubbs, Yang Sun, Steve D Billings, Brian P Rubin. Cleveland Clinic, OH

Background: A wide variety of histologic patterns have been observed in myxoid liposarcoma. The diversity of these patterns can lead to diagnostic difficulty and misclassification, particularly in small biopsy specimens.
Design: We examined the morphologic spectrum of myxoid liposarcoma by cataloguing the patterns identified in the biopsy and resection specimens of 47 primary, recurrent and metastatic tumors in 37 patients.
Results: Patterns identified included: traditional myxoid (94%), traditional round cell (36%), hypercellular myxoid (so-called "transitional") (83%), pseudoacinar (51%), lipoblast-rich (28%), island (26%), stromal hyalinization (17%), lipomatous (17%), cord-like (11%), aggregate (6%), chondroid metaplasia (4%) and HPC-like (2%). Tumors with significant amounts of the lipomatous pattern had large areas that resembled mature adipose tissue potentially leading to misclassification as lipoma or atypical lipomatous tumor. Foci of chondroid metaplasia led to consideration of entities including mixed tumor and cartilaginous neoplasms, while tumors with the cord-like pattern raised consideration for extraskeletal myxoid chondrosarcoma and carcinoma. We also identified two patterns not previously described: aggregate and HPC-like patterns. The aggregate pattern was characterized by grape-like clumps of neoplastic cells in a myxoid background, while the HPC-like pattern consisted of staghorn vessels surrounded by closely packed round cells. The diagnosis of myxoid liposarcoma was confirmed by fluorescence in situ hybridization studies for CHOP (DDIT3) translocation in all cases in which paraffin-embedded tissue was available for analysis.
Conclusions: The morphologic spectrum of myxoid liposarcoma is vast and spans beyond the well recognized traditional myxoid and round cell histologies. Awareness of the variety of histologic patterns in myxoid liposarcoma is critical to avoid misdiagnosis, especially in small biopsy specimens.
Category: Bone & Soft Tissue

Monday, February 28, 2011 1:00 PM

Poster Session II # 25, Monday Afternoon


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