[125] Lipomatous Neoplasms: The Diagnostic and Prognostic Implications of Molecular Classification

H Zhang, ME Johnson, X Wang, AG Nascimento, FH Sim, R Zamolyi, V Pannain, AM Oliveira. West China Hospital, Sichuan University, Chengdu, China; Mayo Clinic, Rochester; Universidade Federal do Rio de Janeiro, RJ, Brazil

Background: The use of molecular techniques has been advocated in differentiating lipomas from atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDL). However, considering that both groups of tumors can recur locally but lack metastatic potential, the practical implication of their molecular characterization has not been scrutinized. The aim of this study was to assess the clinical value of the molecular classification of lipomatous neoplasms.
Design: Four hundred five cases of lipomatous neoplasms diagnosed between 1990 and 2000 and located in the extremities were analyzed for the presence of MDM2/CPM amplification using fluorescence in situ hybridization (FISH). One hundred cells were analyzed in each tumor. Local recurrence-free survival was estimated with the Kaplan-Meier method and compared with the log rank test. Multivariate analysis was conducted using the Cox regression model.
Results: Using solely histologic assessment as criteria, the 405 tumors were classified as lipoma (n=324), intramuscular lipoma (n=29) and ALT/WDL (n=52). After molecular analysis, 11 of the tumors histologically classified as ALT/WDL were reclassified as lipoma (n=5) and intramuscular lipoma (n=6), whereas 7 of the tumors histologically designated as lipoma were reclassified as ALT/WDL. Follow-up information was available for 303 tumors. Prior to the molecular data, the 5-year local recurrence rates for lipoma, intramuscular lipoma and ALT/WDL were 2%, 5% and 45%, respectively (P <0.0001). After molecular reclassification, the 5-year local recurrence rates for lipoma, intramuscular lipoma and ALT/WDL were 1%, 12% and 44%, respectively (P <0.0001). Multivariate analyses showed that histologic type emerged as the only independent risk factor before molecular classification (HRalt=4.15; 95% CI, 1.70-11.13; p=0.0005); however, after molecular classification both histologic subtype (HRalt=2.62; 95% CI, 1.28-5.58, p<0.0001) and type of surgery (HRwle=0.59; 95% CI, 0.36-0.97; p=0.036) correlated with the risk of local recurrence.
Conclusions: The use of molecular testing to complement the histologic assessment of lipomatous tumors more precisely discriminates local recurrence risks for individual groups of lipomatous tumors located in the extremities and therefore provides for appropriate surgical management decisons.
Category: Bone & Soft Tissue

Monday, March 22, 2010 8:00 AM

Platform Session: Section F, Monday Morning


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