Rectal adenocarcinoma metastatic to the thyroid gland.

Metastatic lesions in the thyroid are rarely reported, although microscopic metastasis to the thyroid gland is not uncommon, having been found in 4%-9% of autopsy studies. Here we present a case of rectal adenocarcinoma metastatic to the thyroid. A 28-year-old woman was admitted to the hospital for persistent anal bleeding, weight loss, and dysphagia. Physical and imaging examinations disclosed a nodule in the left lobe of the thyroid and rectal cancer in the upper rectum. Fine-needle aspiration cytology of the thyroid nodule revealed adenocarcinoma, which was consistent with a diagnosis of metastasis from the primary rectal adenocarcinoma to the thyroid. The patient died of tumor recurrence 6 months after surgery. Thyroid metastasis from colon and rectal carcinoma is rare, with only 11 cases appearing in the literature since 1990. The rarity and prognosis of thyroid metastasis from colon carcinoma are discussed here.