[Thyroid Metastasis of Rectal Cancer]

A 65-year-old woman underwent laparoscopic low anterior resection for rectal cancer with distant metastasis to the right lobe of her liver and mediastinal and right subclavian lymph nodes. Since the postoperative chemotherapy resulted in the disappearance of the lymph node metastasis and diminished hepatic metastasis lesion, the enlarged anterior segment of the liver was performed. She was administered chemotherapy for 1 year after the second surgery. Thoracoabdominal computed tomography performed 18 months after the end of the treatment revealed swelling of the left lobe of the thyroid. Ultrasonography showed a 23mm lobulated hypoechoic tumor in the left lobe of the thyroid gland. We suspected thyroid metastasis by aspiration biopsy cytology. Left thyroid lobectomy was performed for definitive diagnosis and local control. Histological examination revealed thyroid metastasis of the rectal cancer. We experienced a rare case of thyroid metastasis from rectal cancer.