Neoplasms of the Thyroid

Overview Thyroid cancer is the most common malignancy of a classical endocrine organ. The most common forms of thyroid cancer derive from follicular thyroid cells, are characterized by cellular and histological patterns (e.g., papillary and follicular thyroid cancer), and are associated with outstanding overall survivorship but a high frequency of disease persistence. Less commonly, thyroid cancers can derive from thyroid neuroendocrine C‐cells (medullary thyroid cancer) that can occur as part of defined genetic syndromes (e.g., multiple endocrine neoplasia type 2). Thyroid cancers can present as or develop into poorly differentiated or dedifferentiated (anaplastic thyroid cancer) that are associated with highly aggressive courses and poor outcomes. Over the past decade, a more individualized approach has been taken for patients with early‐stage thyroid cancer, with reduced emphasis on aggressive surgical approaches, expansion of active surveillance approaches, and reduced use and/or dosing strategies for radioiodine therapy (RAI) using I‐131. RAI, TSH suppression therapy, and for selected local recurrence, reoperation, and external beam radiation therapy remain cornerstones of therapy for patients with progressive or nonremitting forms of thyroid cancer. For those who do not respond to those treatments, or those with specific gene mutations, there has been expansion of options including the use of targeted inhibitors of mutated driver oncogenes in all forms of thyroid cancer, anti‐angiogenic multikinase inhibitors in patients with progressive differentiated thyroid cancers, and immune checkpoint inhibitors.