Occult follicular carcinoma metastasizing to the sinonasal tract.

We report a 34-year-old woman with a clinically occult primary carcinoma of the thyroid metastasizing to the sinonasal tract. The metastasis showed intensive vascularization and involved the nose, the maxillary, ethmoid and sphenoid sinuses, extending to the intracranial cavity. After embolization, the lesion was removed and histopathologically diagnosed as follicular carcinoma of the thyroid. A subsequent total thyroidectomy revealed an 8-mm primary lesion within the left lobe. Thyroid metastases, although rare, need to be considered in the differential diagnosis of hypervascular tumors in the sinonasal tract.