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.
The pattern of HMGA2 rearrangement in the present case of myolipoma is similar to what is found in other benign connective tissue tumor types, including lipomas, i.e., disruption of the HMGA2 locus leaves intact exons which encode the AT-hook domains but separates them from the 3´-terminal part of the gene.
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.
Our data therefore show that a subset of soft tissue osteochondromas shares pathogenetic involvement of HMGA2 with lipomas, leiomyomas and other benign connective tissue neoplasms.
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.
Further cytogenetic studies of pediatric lipoma would be useful to determinate whether some partner genes of HMGA2, such as NFIB, may have a specific role in the early onset of these tumors.
The fact that the examined osteochondrolipoma had a t(12;18) and a HMGA2-SETBP1 fusion identical to the findings in the much more common ordinary lipomas, underscores the close developmental relationship between the two tumor types.
MRI characteristics of lipoma and atypical lipomatous tumor/well-differentiated liposarcoma: retrospective comparison with histology and MDM2 gene amplification.