Polypoid endometriosis with transmural involvement of rectosigmoid colon and forming a 13 cm colonic mucosal mass. Endometriosis shows foci of simple hyperplasia and mucinous metaplasia.
Polypoid endometriosis is endometriotic tissue with histologic features reminiscent of an endometrial polyp or polypoid masses of endometriosis that could simulate a malignant tumor intraoperatively. Two of the earliest well-documented examples were described in the 1950s and involved the colon.
More than half of reported cases occurred in postmenopausal women. Polypoid endometriosis usually involves the ovaries, adnexal soft tissue, uterine serosa, cervix, vagina, ureter, and omentum. The rectosigmoid colon and the ovaries were the 2 most common sites of involvement. Symptoms are related to the effects of a mass, including colonic obstruction, abdominal pain or vaginal bleeding.
Characteristic macroscopic features are polypoid mass. There are variable degrees of cystic change and hemorrhage. Microscopically, endometrial glands and endometrial stroma are identified, with a wide variety of architectural patterns and mild to moderate cytologic atypia. Cystic hyperplasia, cystic atrophy and simple hyperplasia with atypia are frequently seen. Metaplastic epithelium was found in 75% of cases.
Differential diagnoses of polypoid endometriosis include well-differentiated adenocarcinomas, endometrioid adenofibroma, Mullerian (mesodermal) adenosarcoma, and low-grade endometrial stromal sarcoma with glandular differentiation. Well-differentiated adenocarcinomas are characterized by the presence of invasive, cytologically malignant epithelium, and lack of endometrial-type stroma within the tumor. Endometrioid adenofibromas show a fibromatous or ovarian-type stroma but not an endometrial-type stroma. The major architectural feature that distinguishes adenosarcoma from polypoid endometriosis is the presence of stromal cell atypia and periglandular cellular stromal cuffs. Low-grade endometrial stromal sarcoma has a characteristic tongue-like permeative pattern of invasion and, frequently, vascular invasion.
Contributed by Xin Li, MD and Katrina Han, MD