CDK4 and intimal sarcoma: MDM2 (an oncogene that is responsible for blocking the activity of p53) is defined by nuclear overexpression and amplification of the 12q12–15 area, which contains CDK4 (cyclin-dependent kinase inhibitor 2A) and MDM2 [17,18], the MDM2 amplification supporting the diagnosis of intimal sarcoma [17].