We report an unusual case of struma ovarii diagnosed after thyroidectomy for Graves disease and papillary thyroid cancer.
A 46-year-old woman presented with a 3-month history of weight loss, palpitations and irregular periods. Physical examination revealed tachycardia, fine tremor and a diffuse goitre. TSH <0.1 (0.54.2 mU/l), FreeT4 26 (10.819.3 pmol/l) confirmed thyrotoxicosis.
Thyroid ultrasound scan showed a diffusely enlarged gland with an 8 mm solitary nodule in the left lobe and scintigraphy of the neck revealed diffusely increased uptake. Fine needle aspiration cytology of the thyroid nodule was suspicious of a follicular lesion (THY 3). She underwent a total thyroidectomy. Histology revealed a papillary thyroid carcinoma, stage pT4 N1 Mx and the rest of the gland was consistent with Graves disease. Shortly after receiving Radio iodine ablation for the thyroid cancer she became thyrotoxic (TSH<0.01, FT4 54, FT3 13). Post ablation scan showed increased uptake in the lower abdomen.
A CT scan of the pelvis revealed a 13 cm mass originating from the right ovary. She underwent a right salphingo- oophorectomy. The histology of the ovary showed struma ovarii consistent of focally hyperplastic benign thyroid tissue which had completely replaced the normal ovarian tissue.
She remained euthyroid on levothyroxine replacement.
Reports of coexisting Graves disease and struma ovarii or papillary carcinoma and struma ovarii are very rare and we believe this is the first case report confirming the clinical and pathological features of benign struma ovarii, Graves disease and papillary thyroid carcinoma in the same patient. Only 515% of women with struma ovarii develop hyperthyroidism. In our patient it is likely that the high iodine load given for radioablation triggered thyroid tissue hyperactivity in the struma ovarii and subsequent thyrotoxicosis. Ovarian metastasis from thyroid cancer is very rare and in our case there was no such histology evidence.