253 An Insight into a Rare Case of Malignant Struma Ovarii During Pregnancy

Introduction/Objective Struma ovarii (SO) is a monodermal teratoma comprised of > 50% thyroid elements which is rarely associated with secondary malignancy. Patients are often asymptomatic, but a minority of patients present with peritoneal effusions (30%) and hyperthyroidism (10%). Data on pregnancy-associated malignant SO remains scarce, however pregnancy-related hormones are known to stimulate TSH production due to receptor cross reaction which may promote thyroid carcinogenesis . Here, we present a rare case of pregnancy-associated malignant SO, with only seven cases previously reported in the literature. Methods/Case Report 28-year-old woman at 13 weeks gestation presented with a 14 cm ovarian cyst. Laparoscopic cystectomy performed at 16 weeks was complicated by intraoperative spillage. The ovarian cyst was entirely submitted which showed predominantly benign struma ovarii with hypercellular nodules featuring papillary thyroid carcinoma (PTC) nuclear features, including nuclear elongation, irregularity, intranuclear pseudoinclusions, and increased mitoses (up to 4 per 10 HPF). By immunohistochemistry, tumor cells expressed PAX8 and TTF-1 consistent with thyroid differentiation. The pathologic stage was pT1c1. Results NA Conclusion Microscopic examination represents the diagnostic gold standard for MSO which guides subsequent therapeutic management. Careful pathologic examination of struma ovarii is recommended to assess for secondary malignancies, especially those arising in pregnancy.