Pathology of Struma Ovarii: A Report of 96 Cases

Thyroid tissue is a relatively frequent component of mature teratoma and can occur in 5-20 % of cases. Struma ovarii is defined as ovarian goiter which comprises either entirely or predominantly thyroid tissue (> 50 %). This also includes cases of mature teratoma with less than 50 % thyroid tissue but harboring thyroid-associated malignancy. A total of 118 patients with mature teratoma containing thyroid tissue were identified at our institution (1989 to 2014). Ninety-six cases were diagnosed struma ovarii, including 10 cases of papillary thyroid carcinoma, 1 case of highly differentiated follicular carcinoma of ovarian origin (HDFCO), 5 cases of strumal carcinoid, and 80 cases of struma ovarii (53 cases of thyroid-only struma ovarii). Six cases had diffuse adenomatous hyperplasia, and seven cases had focal adenomatous hyperplasia. There was no recurrence on follow-up except one of the papillary thyroid carcinomas. Concurrent primary ovarian lesions included: serous cystadenoma-3, mucinous cystadenoma-4, Brenner tumor-3, thecoma-2, ovarian fibroma-1, and focal hilus cell hyperplasia-4 cases. In this series, papillary thyroid carcinoma and strumal carcinoid were the most common well-differentiated neoplasm/malignancies arising in struma ovarii; these demonstrate a minimal or no aggressive clinical behavior.