Uterine Leiomyosarcoma with a Novel RAB2A-PLAG1 Gene Fusion

Abstract Introduction/Objective Uterine leiomyosarcoma is a malignant neoplasm with three distinct histologic subtypes: spindle, epithelioid, and myxoid. Distinguishing from mesenchymal uterine neoplasms such as endometrial stromal sarcoma can be challenging they may exhibit similar histology immunohistochemical profile. In cases, molecular studies help achieve the definitive diagnosis. It has been shown that ~25% of myxoid leiomyosarcomas harbor TRPS1-PLAG1 RAD51B-PLAG1 gene fusions. To our knowledge, no RAB2A-PLAG1 fusion previously reported in English literature. Methods/Case Report An 80-year-old woman presented abnormal bleeding. A large necrotic mass evident lymphadenopathy was detected on imaging. Endometrial curettage demonstrated positive for CD10, desmin, vimentin lacked expression SMA, SMMH, synaptophysin, chromogranin. AE1/AE3 highlighted rare foci. The patient underwent total hysterectomy bilateral salpingo-oophorectomy. specimen notable 10.8 cm rubbery focally calcified tan- white histologically composed high-grade spindle epithelioid cells hypocellular hyalinized areas. mitotic activity >25/10HPF. Immunohistochemically, neoplastic expressed caldesmon, desmin (patchy), SMA (weak focal), CAM5.2 (patchy) while were negative ER, PR, HMB45, AE1/AE3, WT1, cyclin D1, BCOR, myogenin, pan-NTRK, ALK. P53 staining showed wild type pattern. Histology immunohistochemistry could not definitively differentiate between high grade sarcoma. RNA sequencing identified fusion. light ancillary studies, diagnosis rendered. Results (if Case Study enter NA) NA Conclusion This first case Pathologists should cognizant extensive morphologic immunophenotypic overlap various neoplasms. analysis crucial allowing pathologist to arrive at final