Colon carcinoma metastatic to the thyroid gland.

Metastatic carcinoma to the thyroid gland rarely is encountered in clinical practice; however, autopsy series have shown that it is not a rare occurrence. A case of adenocarcinoma of the colon with metastases to the thyroid is reported. A review of the literature reveals that melanoma, breast, renal, and lung carcinomas are the most frequent tumors to metastasize to the thyroid. Metastatic disease must be considered in the differential diagnosis of cold nodules on radionuclide thyroid scans, particularly in patients with a known primary.