CDK4 and dedifferentiated liposarcoma: WDLPS and DDLPS share the cytogenetic abnormality, specifically amplification of the 12q13-15 region that leads to subsequent diagnostic amplification of MDM2 and CDK4. Previous cytogenetic studies have identified alternative amplification of 1p32 and 6q23 in DDLPS and not identified in WDLPS.