Comprehensive genomic profiling of a unique liposarcoma arising in a patient with Li-Fraumeni syndrome and the novel detection of c-myc amplification: a case report

Background: Germline TP53 mutations have been frequently reported in patients with Li-Fraumeni syndrome (LFS), resulting in a predisposition to various malignancies. Mutations other than germline TP53 mutations can also cause LFS-associated malignancies, but their details remain unclear. We describe a novel c-myc amplification in a unique liposarcoma in a patient with LFS.

Case presentation: A female patient with LFS developed breast cancer twice at the age of thirty; both were invasive ductal carcinomas harboring HER2 amplifications. Computed tomography revealed an anterior mediastinal mass, which was surgically resected. Histological analysis revealed three different lesions corresponding to myxoid liposarcoma-, pleomorphic liposarcoma-, and well-differentiated liposarcoma-like lesions. Fluorescence in-situ hybridization (FISH) analysis did not detect MDM2 amplification, Rb1 deletion, break apart signals of EWS, FUS, DDIT3, or c-myc, or c-myc-IGH fusion signals, but it did detect more c-myc signals. Further FISH analysis and comprehensive genomic profiling revealed c-myc amplification. We considered two differential diagnoses, dedifferentiated liposarcoma lacking MDM2 amplification and myxoid pleomorphic liposarcoma (MPLPS), and determined that this case is most likely MPLPS. However, definite diagnosis could not be made because a clear-cut differentiation of the case from liposarcomas was not possible.

Conclusions: A previous study demonstrated that c-myc amplification could not be detected in various liposarcomas, but the present unique liposarcoma showed c-myc amplification, so the c-myc amplification may indicate that the present liposarcoma is an LFS-related tumor. The present case further clarifies the pathological features of MPLPS and LFS-related liposarcomas by broadening their histopathological and genetic diversities.