Salivary-Like Tumors of the Thyroid: A Comprehensive Review of Three Rare Carcinomas

Thyroid carcinomas represent 3.2% of all new cases of cancer in the United States. Whereas most thyroid tumors arise from follicular cells or, less commonly, parafollicular cells, the derivation of some rare primary thyroid carcinoma subtypes is less clear and represents an area of evolving knowledge. Primary thyroid carcinomas that resemble neoplasms characteristic of the salivary glands (“salivary-like” primary thyroid carcinomas) arguably represent some of the most unusual primary thyroid tumors. Herein, we have undertaken a review of the literature in order to present a comprehensive overview of salivary-like primary thyroid carcinomas including: mucoepidermoid carcinoma, sclerosing mucoepidermoid carcinoma with eosinophilia, and secretory carcinoma. Awareness of these unusual, distinct primary tumors is important for timely diagnosis and optimal patient management. This review highlights these three salivary-like carcinomas, with special emphasis on developments since publication of the World Health Organization (WHO) 2017 Classification of Tumours of Endocrine Organs.