Oral cavity cancer has the eighth highest incidence of newly diagnosed cancers worldwide [1], and squamous cell carcinoma (SCC) accounts for around 90 % of these malignancies [2]. Overall, the incidence of distant metastasis in head and neck SCC at presentation is 10 %, with an additional 20–30 % of patients who develop metastasis later [3]. While nodal involvement is an important prognostic factor in OSCC, distant metastasis affects staging and survival. The most dominant site of distant metastasis is the lungs, closely followed by the liver, bones, and mediastinal lymph nodes [4]. Another location of metastatic OSCC, albeit rare, is the thyroid gland. SCC of the thyroid (SCCT) is a rare type of cancer accounting for 1 % of all thyroid cancers and includes primary SCCT and secondary SCCT, based on the origin of the primary tumor. For a thyroid gland to have a secondary squamous cell carcinoma, there must, by definition, be a primary tumor that metastasized to it. The most common sites for these primary lesions are the esophagus, trachea, and larynx [5]. A comprehensive review of metastatic head and neck SCC cases to the thyroid from April 1984 to May 2017 identified 32 case reports describing this phenomenon [6].

Given the paucity of published cases regarding SCC metastasis to the thyroid and its aggressive molecular biology, an updated review of its pathophysiology, molecular biology, diagnosis, and surgical management is essential. Our review aims to increase awareness of this rare presentation, encourage the development of multidisciplinary, multimodal targeted therapies, and impact surgical practice management guidelines for this disease.