Analysis of SAS gene and CDK4 and MDM2 proteins in low-grade osteosarcoma. The region q13-15 of chromosome 12 contains SAS, CDK4, and MDM2 genes that are rearranged or amplified in a variety of human sarcomas. This study evaluated SAS gene amplification, and MDM2 and CDK4 protein expression in 20 tumor samples of central low-grade osteosarcoma (16 primary, 3 recurrences, 1 lung metastasis). SAS amplification was analyzed by quantitative polymerase chain reaction (PCR), while from the same paraffin-embedded samples, MDM2 and CDK4 protein expression was evaluated by immunohistochemistry. MDM2 and CDK4 proteins were found strongly expressed in 35% and 65%, respectively, of the samples. SAS was found amplified in 15% of the samples. These findings indicate that these genes may be involved in tumorigenesis and progression of low-grade osteosarcoma.