MDM2 and juxtacortical osteosarcoma: After early studies showing amplification of the chromosomal 12q13-15 region (which includes several genes such as MDM2 and CDK4) in some sarcoma types including liposarcomas [14, 15], MDM2 gene amplification, in the form of supernumerary ring and/or giant chromosomes, has been shown to be characteristic of WDL and DDL [16–18]. MDM2 amplification is also associated with other sarcomas such as parosteal osteosarcoma and intimal sarcoma [19, 20], so while it is not entirely specific for WDL and DDL, its assessment by FISH has been developed as an adjunctive tool for their diagnosis [21].