Thyroid cancer (TC) is the most prevalent malignant neoplasm that affects the endocrine system. Hashimoto’s thyroiditis (HT), also known as chronic lymphocytic thyroiditis, is the most common autoimmune thyroid disease (AITD) that, together with Graves’ disease (GD), represent the main autoimmune diseases that affect the thyroid gland. Some studies suggest a greater risk of AITD and the development of TC, while others, investigate its relationship with TC progression and patient prognosis. In this review, we have analyzed published data on the molecular aspects related to the association between AITD and TC, addressing their influence on TC progression, diagnosis, and prognosis of the patients. MEDLINE database (PubMed) platform was used as a search engine and the original articles related to the topic were selected using the keywords combination “thyroid cancer and Hashimoto thyroiditis” or “thyroid carcinoma and thyroid autoimmune disease”. After the selection, we categorized the main findings of the papers into four topics: antitumor immunity, tumor progression, diagnosis, and prognosis. Although most of the studies have pointed out the presence of AITD as a factor that increases the risk of TC, few molecular mechanisms to support this conclusion have been described. Additionally, little information is available to explain, pathophysiologically, the effects of autoimmunity in TC diagnosis, progression, and prognosis.Copyright © 2020 Elsevier GmbH. All rights reserved.