Research progress on the immune microenvironment and immunotherapy of thyroid cancer

Thyroid cancer is the most common endocrine malignancy. Although most patients achieve good prognosis through surgery and conventional treatments, approximately 15%-20% of patients with papillary thyroid cancer and the anaplastic and medullary thyroid cancers still lack effective treatment options. The tumor immune microenvironment plays a critical role in the occurrence, progression, and drug resistance of thyroid cancer. This review focused on the key immune cells in thyroid cancer, including tumor-associated macrophages, myeloid-derived suppressor cells, mast cells, natural killer cells, and T lymphocytes, and explored their roles and mechanisms in tumor immune evasion. Immunotherapy has become an emerging treatment strategy for advanced thyroid cancer, we summarized the attempts and advances in immune checkpoint inhibitors, targeted macrophage therapy and tumor vaccines.