[Metastatic carcinoma of the sigmoid colon to the thyroid gland]

A case of metastatic thyroid cancer from sigmoid colon cancer is presented. A 52-year-old woman had a sigmoidectomy due to adenocarcinoma of the sigmoid colon in April 1988. Serum carcinoembryonic antigen (CEA) levels gradually rose from July 1990 along with multiple metastatic lesions which appeared in the lung. They were resected in January 1991. Two months later the subject noticed a painless and firm lump on the left anterior neck. She was found to have a solitary mass in the left thyroid lobe. Thyroid function remained within normal range. Cytological findings obtained by fine-needle aspiration biopsy showed tall columnar carcinoma cells with an acinar pattern. Subtotal thyroidectomy was performed, and histological examination revealed metastatic adenocarcinoma from colon cancer. Immunohistochemical staining by anti-CEA was positive but anti-thyroglobulin was negative.