Patients with an MDM2-negative lipoma or MDM2-positive WDLPS and a pretreatment T1-weighted MRI scan who were referred to Erasmus MC between 2009 and 2018 were included.
Patients with well-differentiated lipomatous tumors (n = 113), of which 66 were diagnosed as lipoma (mean age 53 years (range, 13-82); 47% women) and 47 as atypical lipomatous tumor (ALT; mean age 60 years (range, 28-88); 64% women), were included into this study using histology and MDM2 amplification status by fluorescence in situ hybridization (FISH) as standard of reference.
In this study, we investigated the utility of MDM2 and p16 along with HMB45 and Melan-A immunohistochemical analysis in distinguishing AML from WDL/DDLS or lipoma.
Although uncommon, MDM2 labeling is seen in a subset of fat-predominant AMLs and is a potential diagnostic pitfall in the evaluation of fatty tumors of the retroperitoneum.
MDM2 amplification is known to occur in a variety of neoplasms and its detection by fluorescence in situ hybridization is helpful in distinguishing well-differentiated and dedifferentated liposarcoma from classic lipoma.
MRI characteristics of lipoma and atypical lipomatous tumor/well-differentiated liposarcoma: retrospective comparison with histology and MDM2 gene amplification.
Moreover, we observed a strong association of malignancy with TP53 mutation, or MDM2 amplification and the presence of a G allele in SNP309, especially in lipoma versus liposarcoma.
We suggest that mdm2 is a marker distinguishing between ordinary lipoma and well-differentiated liposarcoma, and that the genesis of these tumors is different.
Overexpression of mdm2 protein was observed in 6/12 (50%) atypical lipomatous tumours.All lipomas were mdm2-negative. cdk4 overexpression was present in 100% of ALTs.
Amplification of the CDK4 gene without MDM2 amplification was observed in osteosarcomas and a chondrosarcoma but not in soft tissue tumors, whereas amplification of MDM2 gene alone was observed in malignant fibrous histiocytomas (MFHs), liposarcomas, and lipomas, but not in bone tumors.
As for diagnostic significance, the absence of mdm2 and p53 reactivity in lipomas seems to represent a useful marker for differential diagnosis from lipoma-like WD liposarcomas.