Magnetic resonance imaging findings of extrapelvic endometriosis of the round ligament

A 31-year-old woman presented with a mass in her groin accompanied by intense pain during the menstrual period. A poorly circumscribed, elastic, hard mass was palpable in her right inguinal region. Magnetic resonance imaging showed that the mass had continuity with the inguinal course of the round ligament of the uterus. The mass lesion was well enhanced with high intensity on diffusion-weighted imaging. An operation was performed, and the histological diagnosis was endometriosis of the round ligament. After operation, she was completely relieved of pain. It is important to include endometriosis in the differential diagnosis in women with painful inguinal mass lesions at risk for endometriosis.