A case of uterine liposarcoma with PLAG1 rearrangement that was difficult to classify into established subtypes

Herein, we present a case of International Federation of Gynecology and Obstetrics stage IIIB (pT3bNxM0) uterine liposarcoma. Although intensive tumor resection was performed, the patient died 53 days after surgery. The resected surface of the tumor showed a yellowish hemorrhagic infarction. Histologically, adipocytes and lipoblasts were observed in the myxoid stroma. Immunohistochemical examination revealed that the tumor was diffusely positive for PLAG1 (pleomorphic adenoma gene 1) and focally positive for S100 protein and CDK10. The tumor was negative for smooth muscle actin, desmin, MDM2, CDK4, ER, ALK, STAT6, NKX2.2, SS18, DDIT3, BCOR, and pan-TRK. Fluorescence in situ hybridization showed that the tumor had a PLAG1 gene rearrangement. However, further examination using RNA sequencing analysis failed to identify specific sequences. As the tumor was difficult to classify into the four subtypes of liposarcoma, the current disease might be a new type of uterine liposarcoma.