Benign Struma Ovarii in a Patient with Papillary Thyroid Carcinoma: A Rare Case Report

A BSTRACT Struma ovarii (SO) is a rare monodermal ovarian teratoma predominantly composed of thyroid tissue and is usually benign in nature. Functional SO associated with thyrotoxicosis is uncommon, and its coexistence with previously treated papillary thyroid carcinoma may create considerable diagnostic uncertainty due to overlapping clinical, biochemical, and radiological findings. We report the case of a 60-year-old woman with a history of papillary thyroid carcinoma, classical variant, who had undergone total thyroidectomy 2 years earlier. She presented with symptoms of hyperthyroidism and markedly elevated thyroglobulin levels (1560 ng/mL) despite being off levothyroxine therapy. Imaging studies revealed a right ovarian mass suggestive of SO. The patient subsequently underwent total laparoscopic hysterectomy with bilateral salpingo-oophorectomy. Histopathological examination confirmed benign SO. Following surgery, her thyroglobulin levels decreased to 104 ng/mL, and thyroid function normalized after initiation of levothyroxine therapy. She later received low-dose radioiodine ablation at 1.1 GBq. On follow-up, the patient remained clinically and biochemically stable. Benign SO should be considered in postthyrodiectomy patients presenting with unexplained hyperthyroidism and elevated thyroglobulin levels. Early recognition is important to avoid misdiagnosis of metastatic papillary thyroid carcinoma and to guide appropriate surgical and endocrinological management.