Solitary thyroid gland metastasis from rectal cancer: A case report and review of the literature.

Background: Metastatic carcinoma of the thyroid gland is a rare encounter in clinical practice, but autopsy series showed that it is not so rare. Thyroid metastasis from colorectal cancer (CRC) is rare and has a poor prognosis. We herein report a rare case of solitary thyroid metastasis from rectal cancer combined with needle tract implantation after fine-needle aspiration (FNA) of the thyroid nodule and review the relevant literature.