Gynecologic Leiomyosarcoma With Epithelioid Features and PGR::NR4A3 Gene Fusion: First Report in the Vulva.

Vulval leiomyosarcomas with variant features are rare with limited data available in the literature compared to their uterine counterparts. Gynecologic leiomyosarcoma with nuclear receptor 4A3 (NR4A3) gene fusion is a rare, recently described neoplasm that has been reported mostly in the uterus and rarely in the pelvis. Herein, we report the first case of this entity occurring as a primary vulva tumor in a 46-year-old patient. Histologic examination showed a multi-nodular tumor composed of monomorphic epithelioid, rhabdoid and spindled cells arranged in sheets, cords and microcysts within a richly vascularised, myxoid stroma. On immunohistochemistry, the tumor cells were positive for desmin, smooth muscle actin, h-caldesmon, as well as ER and WT1. Gene fusion analysis revealed the presence of a PGR::NR4A3 gene fusion involving exon 2 of PGR and exon 2 of NR4A3 . Local recurrence occurred one year after initial excision. Recognition of this rare subtype of gynecologic leiomyosarcoma in the vulva may help refine the classification of unusual vulvovaginal smooth muscle neoplasms.