A case report of thyroid gland metastasis associated with lung metastasis from colon cancer.

Thyroid gland metastasis of malignant tumors is observed in 1.9% to 9.5% of histologically examined autopsy cases. Thyroid metastasis from colon cancer is extremely rare and the prognosis is poor. Here we report a case of lung metastasis and thyroid gland metastasis following sigmoid colon cancer surgery. In 2000, a 58-year-old woman underwent a sigmoid colectomy for sigmoid colon cancer. In 2005, a metastatic lung tumor was detected by chest CT. The patient underwent a partial thoracoscopic resection of the left lung in April 2005. On a CT scan taken 3 years and 4 months after the lung resection, a tumor mass was observed in the left lung and a low-absorption region with an unclear border was seen in the left lobe of the thyroid gland. Thyroid aspiration cytology showed adenocarcinoma, and a diagnosis of thyroid gland metastasis from sigmoid colon cancer was made. In April 2008 a subtotal thyroidectomy was performed. Following surgery, the patient underwent chemotherapy with mFOLFOX6 and bevacizumab. Nevertheless a number of lung metastases and expressions of lung metastasis were subsequently observed. Histopathological examination revealed a number of metastases of differentiated papillary adenocarcinoma in the thyroid gland from colon cancer.