Colon cancer metastatic to the lung and the thyroid gland.

The clinical diagnosis of primary thyroid cancer is uncommon, constituting 1.5% of all cancers in the United States. Clinically diagnosed metastatic cancer to the thyroid gland is rare. Colon cancer is one of the most common cancers in the United States, with a high propensity to metastasize; 30% to 40% of patients have metastatic disease at the initial diagnosis. The most common sites of metastasis from colon cancer are the regional lymph nodes, the liver, the lung, and the peritoneum. Colon cancer metastasis to the thyroid gland is rare, with only a few reported cases, mainly in the pathology literature. These cases describe metastasis from colon cancer to the thyroid gland that became apparent years after the initial diagnosis of colon cancer and were usually associated with dissemination to the liver, the lung, or both. We report a case of colonic adenocarcinoma metastatic to the thyroid gland and lung without involvement of the liver. A review of the literature is also included.