Endometrioma of the Rectum Simulating Carcinoma

ENDOMETRIOSIS IS a condition in which endometrial tissue exists in an ectopic location. Although benign, it may grow and exhibit invasive and metastatic properties as long as ovarian stimulation persists. Symptoms tend to be more severe during the menses, although this is not invariably true. Endometriosis of the rectum or rectosigmoid is not uncommon and may be difficult to distinguish from carcinoma. A positive diagnosis prior to operation is apparently rare. Symptoms may vary from mild diarrhea to complete intestinal obstruction, and on rare occasions blood may appear in the stools during the menses. The diagnosis of any tumor occurring in this location should be established histologically before major resections of bowel are undertaken, if needless radical surgery is to be avoided. The following case is presented because of the unusual size and location of a huge endometrioma, which clinically and radiographically was thought to be a carcinoma of the