Thyroid Metastasis

Epidemiology

Metastasis to the thyroid gland is rare but well documented. The thyroid gland is the second most richly vascularized organ, with a blood flow of 560 mL/100 g of tissue/minute. Compared with other organs, it is relatively immune to secondary deposits. The most common sites of origin are the kidney, breast, lung, and skin (melanoma), which account for 70% of reported cases. Colonic, prostate, or nasopharyngeal carcinoma metastases in the thyroid gland have also been documented.

Clinical Findings

Thyroid metastasis may present as a mass; difficulty in breathing, swallowing, or talking; or stridor. Clinical examination may reveal a thyroid mass whereas endoscopic examination may show tumor within the larynx as a result of extrathyroid spread.