Metastasis of a rectal adenocarcinoma to the thyroid gland: diagnostic and therapeutic implications.

Background: Overt metastasis from solid tumors to the thyroid gland is a rare finding. Carcinomas that metastasize most often originate from kidney, breast and lung. Only single cases of metastasis from the gastrointestinal tract have been reported. We describe a rare case of metastasis to the thyroid gland from a rectal adenocarcinoma which had been treated by rectum extirpation and a combined radiochemotherapy seven years earlier. Since the lesion in the thyroid gland was the only tumor manifestation in this patient, total thyroidectomy was performed.

Conclusions: In patients with a history of cancer, primary neoplasms of the thyroid gland are not likely to be the cause of a thyroidal tumor. Fine-needle aspiration biopsy is the appropriate diagnostic procedure to define the histological diagnosis. Potentially curative resection should be performed if metastasis to the thyroid gland is the only tumor manifestation. Palliative chemotherapy should be considered if additional tumor manifestations are detected.