Additionally, although not entirely specific, strong and diffuse, nuclear SATB2 immunostaining characterizes more than 90% of osteosarcomas [75–77], while confirmation of MDM2 and CDK4 amplification by FISH or immunohistochemistry may be diagnostically helpful in cases of parosteal or central osteosarcoma exhibiting low-grade cytomorphology, thus imitating benign fibro-osseous lesions of the jaws [78–82]. The gene discussed is CDK4; the disease is osteosarcoma.