Malignant Hurtle cell struma ovarii: oncocytic thyroid carcinoma arising in an ovarian dermoid

Abstract

Mature cystic teratoma, also known as ovarian dermoid cyst, is the most common ovarian germ cell tumour, accounting for 20% of ovarian neoplasms. Most are benign, with malignant transformation occurring in 1–2% of cases. Transformation to thyroid carcinoma is rare and usually of papillary subtype. Here we report a case of oncocytic (Hurtle cell) thyroid follicular carcinoma arising from a mature cystic teratoma. The patient presented with post-menopausal bleeding and underwent a salpingo-oophorectomy. Histological examination revealed the mass to be a struma ovarii dermoid cyst with an oncocytic thyroid carcinoma infiltrating into the surrounding ovarian parenchyma. To our knowledge this is the first report of follicular thyroid carcinoma with widespread oncocytic differentiation in the literature.