Metastasis of squamous cell carcinoma of the head and neck to the thyroid: a single institution's experience with a review of relevant publications.

The thyroid gland is a rare site of metastasis, and in particular of those of squamous cell carcinoma (SCC) from the head and neck region. We have reviewed the aetiology, pathogenesis, clinical characteristics, radiological features, immunohistochemical profile, prognosis, and management of metastatic SCC from the head and neck region to the thyroid, and searched current publications on the Medline, Embase, and Cochrane databases using the following keywords: "SCC of thyroid", "secondary SCC of thyroid", and "metastasis to the thyroid", for papers published during the last 33 years (April 1984 to October 2017).We found a total of 19 papers that reported a total of 32 cases that were relevant. Four further cases were discovered as an incidental finding on follow-up positron emission tomographic/computed tomographic scans with magnetic resonance imaging of the head and neck at our hospital, which were confirmed with an ultrasound-guided core needle biopsy followed by immunohistochemical examination. For patients who are doing well, whose disease is controlled at the primary site, and who have no evidence of distant metastatic disease, total thyroidectomy could be considered followed by adjuvant radiation or chemoradiotherapy, depending on the presence of intermediate or high-risk features on pathological examination and previous history of radiation. This may help to control the disease and avoid local morbidity.