MDM2 copy numbers in well-differentiated and dedifferentiated liposarcoma: characterizing progression to high-grade tumors.

[well-differentiated liposarcoma]

MDM 2 gene amplification is associated with well-differentiated (WDL ) and dedifferentiated liposarcomas (DDL ). Using fluorescent in situ hybridization (FISH ), we sought to characterize various patterns of MDM 2 amplification among the morphologic spectrum of liposarcoma .Forty -six cases of liposarcoma in various sites were examined and included 22 WDLs , 14 DLLs , and 10 negative control subjects .The MDM 2 amplification ratio (MDM 2 /CEP 12 ) was lower in WDL (10 .2 ) compared with DDL (18 .3 ) cases (P = .0000002 ). An amplification ratio of 16 showed optimal sensitivity (0 .86 ) and specificity (0 .96 ) as a cutoff point for progression to DDL . Borderline areas , defined as tumors with increased cellularity and atypia but with preserved lipomatous differentiation , showed a significantly higher MDM 2 ratio (17 .5 ; P = .0007 ) compared with WDL . Central (retroperitoneal and intra-abdominal ) tumors also showed a significantly higher MDM 2 ratio than peripheral ones (P = .02 ).Differences in MDM 2 amplification profiles among liposarcomas could help further define and predict progression to high -grade neoplasia .