A rare case of follicular thyroid carcinoma in ovarian struma

Struma ovarii is a form of specialised mature teratoma, with predominantly mature thyroid tissue in an ovarian teratoma as seen in 2% of cases. Its malignant transformation is even rarer and is seen in only 5% of those cases. This 40-year-old female patient had an incidental finding of a pelvic mass during investigation of secondary amenorrhoea. She underwent a staging laparotomy and pelvic clearance. The histopathology revealed a bilateral mature teratoma of the ovary with follicular thyroid carcinoma in the right ovarian struma (malignant struma). A total thyroidectomy was performed followed by a whole body 31I scintigraphy which did not reveal any abnormal uptake of isotope. The patient remains well after four years and is being followed-up with serial serum thyroglobulin surveillance.