Well-differentiated liposarcoma primary from thymic stroma: Case report and literature review

Primary liposarcoma of thymic stroma is an exceptionally rare tumor. Histological findings are often definitive for diagnosis, however due to the variability of nuclear atypia and the overlapping with other adipocytic tumors, ancillary techniques are helpful as confirmatory tools. Currently, Fluorescent in situ hybridization for MDM2 is the gold standard for diagnosis of well-differentiated and dedifferentiated liposarcomas, however a panel of immunohistochemical stainings, including MDM2, CDK4 and p16 is available as alternative method, helping to distinguish liposarcoma from its benign counterpart lipoma, especially in borderline cases. We describe the case of a young female diagnosed with a well-differentiated lipomatous tumor primary of thymic stroma with near cut-off result for MDM2-FISHand positive immunohistochemical staining for the panel described above. We discuss the challenges in the diagnosis of this rare entity andpresent an updated literature review.