[Rectal endometriosis: entity difficult to diagnose.]

Endometriosis is a gynecologic disorder characterized by the presence of endometrial glands and stroma outside the endometrial cavity and the uterine musculature. Although the ectopic endometriotic implants are most commonly found in the pelvis, the GI tract is the most common site of extrapelvic endometriosis The diagnosis of rectosigmoid is difficult to make on colonoscopy because of the subepithelial location of the endometriotic implants. We present a case report ofa 38-years-old woman referred with a diagnosis of rectal cancer with large intestine symptoms.Rectal endometriosis should be considered in the differential diagnosis of extramucosal rectal masses in premenopausal women, particularly if the patient has gynecological complaints or a history of infertility.