941 Primary ovarian hydatid cyst: an uncommon presentation mimicking ovarian malignancy

Introduction/Background Echinococcosis, a parasitic infection caused by Echinococcus granulosus, typically manifests in the liver and lungs. Intra-abdominal hydatid dissemination can arise from accidental rupture of the hydatid cyst within the peritoneal cavity, leading to secondary echinococcosis. However, primary pelvic hydatid cysts are exceptionally rare, accounting for less than 0.5% of all hydatid cysts. Methodology We present the first case of primary ovarian hydatid cyst treated at our institution in 2023. Results A 43-year-old woman without significant medical history presented with persistent abdominopelvic pain. Clinical examination revealed a 10 cm renitent, mobile pelvic mass. An abdominopelvic MRI demonstrated a 13.5x12x5 cm cystic mass with a thick wall and parietal nodular formations extending from the right ovary. Three cystic lesions in the liver suggested biliary cysts. Due to the size of the biliary cysts on MRI, hydatid serology was requested, which returned negative. The CA-125 tumor marker level was 50 U/mL. Following a multidisciplinary discussion, the patient underwent an exploratory laparotomy. Intraoperatively, a 15 cm pelvic cystic mass of adnexal origin was identified. Right adnexectomy was performed. Extemporaneous histological examination confirmed a hydatid cyst. Subsequently, peritoneal toileting with hypertonic serum was performed. The patient's postoperative course was uneventful, and she was discharged five days after surgery with referral to the infectious diseases department for further management. Conclusion Despite their rarity, hydatid cysts should be considered in the differential diagnosis of well-circumscribed ovarian cysts on ultrasound, particularly in endemic regions. These cysts are often misdiagnosed as ovarian cysts or tumors but can be effectively managed with radical excision and medical therapy. Disclosures None.