After a round of screening followed by repeat assessment using probes for each exon of TSC1 and TSC2, the osteosarcoma cell line CAL-72 showed homozygous deletion of exons 6 to 23 of TSC1; and the hepatocellular carcinoma cell line SNU-398 showed homozygous deletion of exons 10–41 of TSC2. This evidence concerns the gene TSC2 and osteosarcoma.