Endomyometriosis ("Uterus-like mass") in an XY Male: Case Report With Molecular Confirmation and Literature Review

Male endometriosis and endomyometriosis (also termed "uterus-like mass") are 2 unusual manifestations of endometriosis. We report a case of male endomyometriosis with immunohistochemical and molecular confirmation. A 52-year-old man presented with stabbing pelvic pain. Computed tomography scan showed a mass in the right inguinal area, at the site of prior hernia repair. The lesion was tubular in shape, with a thick muscular wall and a central blood-filled lumen. Microscopically, the tissue showed layers of concentric smooth muscle, with endometrial glands and stroma lining the lumen. Many theories have been proposed regarding the etiology of both endomyometriosis and male endometriosis, including remnant rests of Müllerian tissue and metaplasia. Cases of male endometriosis typically have been linked to estrogen therapy for prostate cancer. Our patient had a history of cirrhosis and took spironolactone, possibly leading to an altered hormonal state that interacted with a reactive/metaplastic process at a site of prior surgery.