Malignant degeneration of rectal endometriosis

Endometriosis is a relatively common disease among women with child-bearing potential, and rare before puberty or following menopause. It consists of the presence of hormone-responsive endometrium outside the endometrial cavity.

We report the case of a patient with a rectal lesion, initially approached as a primary rectal malignancy, where histopathology eventually revealed an adenocarcinoma arising from endometrial tissue in the colonic wall.

Endometriosis has an estimated rated of 10-20%. Sites may be split up into two larger categories - gonadal and extragonadal. The frequency of extragonadal endometriosis in the bowel is estimated to involve 3%-37% of women with pelvic endometriosis, and most lesions are found in the sigmoid colon and rectum. The malignant transformation of endometriotic lesions is estimated between 0.3% and 1% of cases. The gold standard in the diagnosis of intestinal endometriosis is exploratory laparotomy and the pathological study of specimens. Adjuvant radiotherapy and chemotherapy, although used for some patients, have not proven effective.