[62] Fluorescence In-Situ Hybridization for 12q15 Is a Useful Tool To Distinguish Undifferentiated Pleomorphic Sarcoma from Dedifferentiated Liposarcoma

S Chopra, D Lopez-Terrada, AJF Lazar, WL Wang. M.D. Anderson Cancer Center, Houston, TX; Baylor College of Medicine/Texas Children's Hospital, Houston, TX

Background: Well differentiated liposarcomas have ring and giant marker chromosomes harboring amplification of 12q13∼15 region. Fluorescence in-situ hybridization (FISH) for 12q15 amplification differentiates lipomas and atypical lipomatous tumors/well differentiated liposarcomas. We retrospectively review the clinical utility of FISH for 12q15 amplification to distinguish undifferentiated pleomorphic sarcoma (UPS) and cellular & dedifferentiated liposarcoma (DL).
Design: 16 cases ultimately diagnosed as 13 DL and 3 cellular liposarcomas were clinically evaluated with 12q15 FISH for confirmation; for comparison, 18 UPS were obtained from institutional files. In all cases, FISH was performed on unstained FFPE slides using a homebrewed 12q 15 probe and a commercial centromere 12 probe. In each case, 100 cells with ≥2 CEP12 signals were counted and amplification defined as 12q15:CEP12 ratio ≥2.5.
Results: The cellular/DLs (3 biopsies, 13 resections) involved: retroperitoneum (n=12), extremities (n=2), hip (n=1) and testicular region (n=1). All 16 cases of cellular/DLs were positive for 12q15 amplification by FISH. 8 of the 16 cases were initially considered UPS on morphologic grounds, but had 12q15 amplification demonstrated and were ultimately confirmed to be cellular or DL on with review of additional pathology slides from other cases or combined with radiologic features. The 18 UPS (3 biopsies, 15 resections) involved: extremities (n=9), retroperitoneum/pelvis/abdomen (n=6), scrotum/spermatic cord (n=2) and back (n=1). 3 of 17 (18 %) UPS cases showed 12q15 amplification. These 3 cases occurred in the abdomen, retroperitoneum and spermatic cord and could indeed represent DL with no confirming adipocytic component found.
Conclusions: Although location and radiological findings can be a useful to separate DL from UPS, these are not always sufficient. FISH for 12q15 amplification is a useful adjunct tool in distinguishing DL from UPS in certain cases lacking clear adipocytic differentiation, particularly biopsies. Lack of 12q15 amplification effectively excludes a diagnosis of DL and 12q15 amplification, while perhaps not specific, indicates that DL should be strongly considered. This test has clinical utility in distinguishing UPS from DL as the natural histories of these two neoplasms vary significantly in patterns of local/distant recurrence and outcome.
Category: Bone & Soft Tissue

Monday, March 22, 2010 1:00 PM

Poster Session II # 15, Monday Afternoon

 

Close Window