Struma ovarii is a rare taratoma that accounts for 0.5 -1% of all ovarian tumors. It is sometimes difficult to differentiate struma ovarii from ovarian carcinoma. We encountered a case of struma ovarii that was suspected to be malignant due to the accumulation of massive ascites and an elevated CA125 level. It was successfully treated with laparoscopic surgery. A 37 -yearold nulliparous woman consulted a local physician with a chief complaint of abdominal distention. Computed tomography (CT) of the abdomen revealed a pelvic tumor with a large amount of ascites. She was referred to our department. Contrastenhanced magnetic resonance imaging (MRI) and CT showed bilateral ovarian tumors with multicystic and solid components. CA125 level was markedly elevated. Two cytological examinations of ascites showed no malignant cells. Preoperatively, malignancy was strongly suspected, but considering the possibility of a benign ovarian tumor, laparoscopic surgery was scheduled. During laparoscopic surgery, 4,850 mL of ascites were aspirated, and the left adnexa was removed. Intraoperative rapid pathology suggested struma ovarii with no evidence of malignancy. Postoperative pathology showed mature teratoma and struma ovarii. Although struma ovarii is benign in 90 -95% of cases, there have been scattered case reports in which suspected malignancy led to unnecessary or excessive surgery. We propose that appropriate preoperative imaging and accurate intraoperative rapid pathology can prevent excessive surgery, conservative or laparoscopic excisions should be considered.

Polypoid endometriosis is a rare form of endometriosis characterized by polypoid masses that histologically often resemble endometrial polyps. We report a case of rapidly progressing polypoid endometriosis that was preoperatively assumed to be advanced ovarian cancer. A 46 -yearold woman, 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 contrastenhanced) showed masses in the right adnexa, cecum, sigmoid colon, and omentum, and PET -CT demonstrated increased uptake, suggesting ovarian cancer and peritoneal dissemination. The patient later developed intestinal obstruction, and colonoscopy revealed multiple polypoid 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 treatment. Second laparotomy was then performed for right adnexal tumor resection and ileocecectomy. Pathological examination revealed polypoid endometriosis extending from the ovary to the cecal 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 patients in their 40s and 50s. It is a benign disease but is often difficult to distinguish from malignancy preoperatively because it rapidly forms numerous solid lesions. Although polypoid endometriosis is rare, with no specific imaging findings, including it in a differential diagnosis may facilitate preoperative identification.

We describe four cases of pseudomyxoma peritonei (PMP) that were diagnosed and treated at our hospital. Case 1 : A 26 -yearold woman with a large multicystic ovarian tumor and massive ascites was diagnosed with PMP originating from a borderline mucinous ovarian tumor. She underwent fertilitypreserving staging laparotomy and was treated with three courses of intraperitoneal chemotherapy. There has been no recurrence in the 15 years since her first operation. Case 2 : A 72 -yearold woman with a giant ovarian tumor and massive ascites was diagnosed with PMP originating from lowgrade appendiceal mucinous neoplasm (LAMN). After laparotomy, the patient was managed conservatively because she did not want aggressive treatment. She has remained asymptomatic with a small amount of ascites for 3 years. Case 3 : A 82 -yearold woman with ovarian tumors, massive ascites, and suspected PMP underwent emergency laparotomy due to appendiceal perforation and panperitonitis. She was diagnosed with PMP originating from LAMN. She has remained asymptomatic with a small amount of ascites for 2 years. Case 4 : A 42 -yearold woman with multicystic ovarian tumors and massive ascites underwent laparotomy. She was diagnosed with PMP originating from LAMN. Since multidisciplinary treatment was indicated and desired, the patient was referred to a specialized facility where cytoreductive surgery and hyperthermic intraperitoneal chemotherapy was performed. The patient has done well since the treatment. Although most cases of PMP originate from mucinous tumors of the appendix, female patients with PMP often present with ovarian tumors and are commonly referred to gynecology clinics. It is therefore important for gynecologists to be familiar with PMP and to be able to diagnose it accurately and select the most suitable management including multidisciplinary treatments.