CDK4 and gastrointestinal stromal tumor: Amplification of MDM2 was detected in one case, by FISH, and by qRT-PCR, the same case showed moderate expression, compared with a dedifferentiated liposarcoma positive control, of both MDM2 and CDK4, a gene well known to be amplified in dedifferentiated liposarcoma and described to be not amplified in GIST [27].