Distinction between lipoma and liposarcoma by MDM2 alterations: A case report of simultaneously occurring tumors and review of the literature

We investigated a lipoma and a well-differentiated/dedifferentiated liposar coma (WD/DDL), occurring simultaneously in one patient for the possible rol e of p53 and mdm2 in the molecular oncogenesis of liposarcoma and tumor pro gression. The hypothesis tested was if there is a continuum in the developm ent from lipoma to liposarcoma. Lipoma was characterized by a lack of p53 m utation, p53 LOH and p53 protein expression, as well as by mdm2 amplificati on and mdm2 protein expression. p53 mutation and p53 LOH were found neither in the well-differentiated nor in the dedifferentiated parts of the liposa rcoma. In contrast, mdm2 amplification and an increase in mdm2 protein expr ession were found to be associated with malignancy and dedifferentiation, w hereas p53 protein expression was only slightly increased. These findings i ndicate that mdm2 constitutes one of the most common targets for molecular aberration in WD/DDL. We suggest that mdm2 is a marker distinguishing betwe en ordinary lipoma and well-differentiated liposarcoma, and that the genesi s of these tumors is different.