Malignant transformation of intestinal endometriosis is a rare event with an unknown rate of incidence. Metachronous progression of endometriosis to adenocarcinoma from two distant intestinal foci happening in the same patient has not been previously reported.
We describe a case of metachronic transformation of ileal and rectal endometriosis into an adenocarcinoma occurring in a 45-year-old female without macroscopic pelvic involvement of her endometriosis. First, a right colectomy was performed due to intestinal obstruction by an ileal mass. Pathological examination revealed an ileal endometrioid adenocarcinoma and contiguous microscopic endometriotic foci. Twenty months later, a rectal mass was discovered. An endoscopic biopsy revealed an adenocarcinoma. En bloc anterior rectum resection, hysterectomy and bilateral salpingectomy were performed. A second endometrioid adenocarcinoma arising from a focus of endometriosis within the wall of the rectum was diagnosed.
Intestinal endometriosis should be considered a premalignant condition in premenopausal women.
The development of a malignancy is a relatively common complication of endometriosis . In fact, several publications have reported malignant neoplasms arising from endometriosis. Most of these publications are case reports or refer to a small series of patients presenting either ovarian carcinomas with associated endometriosis or invasive endometrioid adenocarcinomas involving adjacent pelvic structures . Malignant transformation of extraovarian endometriosis, including the intestinal tract, however, has not been reported as frequently . The largest reported series of neoplastic changes in gastrointesinal endometriosis includes 17 cases  We describe a case of metachronic malignant transformation arising from two different intestinal endometriotic sites, ileal and rectal, occurring in the same patient.
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