A case of polypoid endometriosis mimicking advanced ovarian carcinoma with rapid growth, invasion, and dissemination

Polypoid endometriosis is a rare form of endometriosis characterized by polypoid masses that histo-logically often resemble endometrial polyps. We report a case of rapidly progressing polypoid en-dometriosis that was preoperatively assumed to be advanced ovarian cancer. A 46 -year -old wom-an, para 0, underwent laparoscopic myomectomy and left adnexectomy for uterine fibroids and a left ovarian endometrial cyst after administration of gonadotropin releasing hormone (GnRH) agonist for 4 months. Eleven months postoperatively, rapid right ovarian enlargement occurred. CT and MRI (both contrast -enhanced) showed masses in the right adnexa, cecum, sigmoid colon, and omen-tum, and PET -CT demonstrated increased uptake, suggesting ovarian cancer and peritoneal dissem-ination. The patient later developed intestinal obstruction, and colonoscopy revealed multiple pol-ypoid lesions in the sigmoid colon. The omental tumor and right adnexa were biopsied during exploratory laparotomy, and diagnosed as polypoid endometriosis with no malignancy by permanent pathology. The right adnexal tumor shrunk markedly after 4 months of GnRH antagonist treat-ment. Second laparotomy was then performed for right adnexal tumor resection and ileocececto-my. Pathological examination revealed polypoid endometriosis extending from the ovary to the ce-cal mucosa. The patient has been asymptomatic for over 1 year postoperatively. The sigmoid colon tumor shrunk but is still present.Polypoid endometriosis predominantly affects the ovaries, colon, peritoneum, and omentum of pa-tients in their 40s and 50s. It is a benign disease but is often difficult to distinguish from malignan-cy preoperatively because it rapidly forms numerous solid lesions. Although polypoid endometrio-sis is rare, with no specific imaging findings, including it in a differential diagnosis may facilitate preoperative identification.