CDK4 and sarcoma: One of the first actionable molecular alterations discovered in sarcomas has been the amplification of the chromosomal region encoding the murine double minute 2 (MDM2) and cyclin dependent kinase 4 (CDK4) genes in a subset of liposarcomas (well-differentiated and dedifferentiated liposarcomas; WDLPS and DDLPS) (9, 10).