Uterine tumor resembling high-grade endometrial mesenchymal sarcoma with GATAD2B-MMRN1 fusion

Uterine sarcomas are a group of rare malignant tumors of mesenchymal tissue of the uterus, and their diagnosis is often difficult because they have variable morphologies and no typical immunophenotype. This report describes a 48-year-old woman who underwent laparoscopic myomectomy and relapsed within 5 years with a large mass in the pelvic cavity. Morphologically, the tumor was composed of oval cells and small arteries, and the cells showed moderate to severe atypia. Immunohistochemical results showed that the tumor cells expressed desmin, smooth muscle actin, and h-caldesmon, which supported myogenic differentiation. They were strongly positive for Cyclin D1, estrogen receptors (ER), and estrogen receptors (PR), supporting their origin from uterine mesenchymal cells. Next-generation sequencing (NGS) revealed a GATAD2B::MMRN1 rearrangement. The patient was diagnosed with uterine sarcoma resembling high-grade endometrial mesenchymal sarcoma with a GATAD2B-MMRN1 fusion. We review the relevant literature and discuss the diagnostic and differential diagnostic points for this disease.