Mullerianosis or Müllerian choristomas are developmental alterations that consist of an organoid structure with normal Müllerian tissue. We present a 62-year-old patient diagnosed on ultrasound scanning and on CT scan of bilateral ovarian cysts. During surgery, a left ovarian cyst and retroperitoneal tumor (adhered to sigmoid serous surface) were found. On histological examination, the tumor corresponded with a Müllerian choristoma showing endometrial, endosalpingeal and endocervical epithelium, with foci of intestinal metaplasia, a phenomenon not described in the literature.