MDM2 and liposarcoma: ALT/WDL and dedifferentiated liposarcomas (DDL) most often have a supernumerary ring and giant marker chromosomes composed of amplified sequences from the 12q13-15 region [9,10], including the murine double-minute type 2 gene (MDM2) and the cyclin-dependent kinase 4 gene (CDK4) [11-13].