Incidental diagnosis of struma ovarii after thyroidectomy for thyroid cancer: functional imaging studies and follow-up.

BACKGROUND: Struma ovarii is a rare ovarian germ-cell tumor containing thyroid tissue. We report an unusual case of incidental diagnosis of struma ovarii after thyroidectomy for thyroid cancer.

CASE: A 24-year-old woman presented with a papillary thyroid carcinoma (pT3N1). After (131)I administration for thyroid remnant ablation, whole-body scan showed a thyroid bed uptake and a right pelvic uptake corresponding to an ovarian cyst on ultrasonography. Preablation thyroglobulin was more elevated than usually found after total thyroidectomy. (18)F-FDG PET was normal. Histopathological analysis revealed a benign struma ovarii. At 6 months, after oophorectomy, serum-stimulated Tg returned to undetectable value and diagnostic WBS was negative.

CONCLUSION: Only few cases of incidental scintigraphic diagnosis of struma ovarii have been described. To our knowledge, it is the first case revealed after remnant ablation for thyroid carcinoma. The distinction with ovarian metastasis is discussed.