A Case of Incidental Struma Ovarii Confounded with the Metastasis of Papillary Thyroid Cancer

ABSTRACT

A focal radioactive iodine uptake in the pelvis of a patient with differentiated thyroid cancer needs differential diagnosis besides bone metastasis. Struma ovarii is a rare monodermal ovarian teratoma composed predominantly of mature thyroid tissue; 5-10% of these tumors are malignant. As diagnosis and surgery of thyroid cancer have increased recently, incidental cases of struma ovarii, after radioactive iodine treatment, were occasionally reported. Rare cases of ovary metastasis of thyroid cancer were also reported. We report a case of benign struma ovarii incidentally found in a patient with papillary thyroid cancer. The patient showed a sustained high level of thyroglobulin and focal radioactive iodine uptake in the right pelvis, confused with distant metastasis, after total thyroidectomy and radioactive iodine treatment.