Colorectal cancer metastasis to the thyroid.

A 69-year-old Japanese woman underwent a curative operation for rectal cancer (T2, N0, M0, Dukes B, R0, and stage IIA of American Joint Committee on Cancer) 3 years ago. On subsequent routine follow-up, a right-side thyroid nodule and a regional lymph node of up to 1.5 cm in diameter was palpated. FDG-PET demonstrated high FDG accumulation in the right lobe of the thyroid gland, neck lymph nodes, and sacral periosteum. We diagnosed a local recurrence of rectal cancer and a primary thyroid cancer. We chose radiotherapy for the periosteal recurrence, and then right hemithyroidectomy with regional lymph node dissection for the thyroid tumor was performed. Pathological examination demonstrated mucinous carcinoma, the same as the previous surgical specimen from the rectum. She had been treated with postoperative chemotherapy and had been alive and well for 26 months with lung metastases. Although thyroid gland metastasis from colorectal cancer is rarely reported, physicians should consider the possibility of thyroid gland metastasis when performing routine follow-up examinations for recurrence of colorectal cancer.