TP53 and dedifferentiated liposarcoma: In retroperitoneal WDLPS/DDLPS tumors MDM2 amplifications and p53 mutations were mutually exclusive but in non-retroperitoneal DDLPS tumors p53 mutations occur in the presence of MDM2 amplifications.9, 10 The latter implicates a role for mutant p53 in the dedifferentiation process.