The patient was a 40-year-old woman with right lower abdominal pain that occurred during menstruation only who had no history of endometriosis. Her McBurney's point was positive with abdominal guarding and rigidity. Gynecological examinations showed normal results. Her menstrual cycles were regular. Abdominal computed tomography and ultrasonography showed a 30 mm mass involving the ileocecal junction that was suggestive of an appendiceal abscess.The patient underwent resection of the bowel segment affected by the disease, followed by anastomosis of the ileum and ascending colon for immediate restoration of intestinal transit. Histological analysis confirmed the diagnosis of endometriosis. The patient remains asymptomatic in 20 months of follow-up after surgery.