Multifocal hyperfunctioning thyroid carcinoma without metastases.

Hyperthyroidism due to thyroid carcinoma is rare, and most cases are caused by hyperfunctioning metastatic thyroid carcinoma rather than primary carcinoma. Among primary hyperfunctioning thyroid carcinoma, multifocal thyroid carcinoma is exceedingly rare, with the only one case being reported in the literature. Here, we describe the case of a 62-year-old woman with multifocal functioning thyroid carcinoma. Technetium-99m (99m Tc) scintigraphic imaging showed four hot areas in the thyroid gland. Histopathological examination of all four nodules revealed papillary carcinoma, corresponding to hot areas in the 99m Tc scintigram. DNA sequencing of the thyrotropin receptor (TSH-R) gene from all nodules revealed no mutation, indicating that activation of TSH-R was unlikely in the pathophysiogenesis of hyperfunctioning thyroid carcinoma in the present case.