CDK4 and liposarcoma: With the exception of the spindle cell variant, all well-differentiated liposarcoma subtypes share the same genetic aberration and are characterized by supernumerary ring and/or giant rod chromosomes containing amplified segments from the 12q13-15 region where several proto-oncogenes including murine double minute type 2 (MDM2), cyclin-dependent kinase 4 (CDK4), high-mobility AT-hook 2 (HMGA2), and tetraspanin 31 (TSPAN31 or SAS) are located (61–69).