The prevalence of thyroid cancer, the most common malignancy originating from an endocrine organ, has increased worldwide and many studies have been conducted to evaluate the risk factors for thyroid cancer. Inflammation could be a potential risk factor for cancer development, so the association of autoimmune thyroid disease (AITD) with thyroid cancer have been studied; however, there are still controversies.
Among AITDs, Hashimoto's thyroiditis (HT), known as chronic lymphocytic thyroiditis, is the most common, followed by Graves' disease (GD). Therefore, most studies have been conducted on the relationship between Hashimoto's thyroiditis or Graves' disease and thyroid cancer. Most of previous studies and meta-analysis revealed that HT was a risk factor of thyroid cancer. Interestingly, recent studies have shown less aggressiveness and better outcome of concurrent thyroid cancer in patients with HT, even though HT increases the risk of thyroid cancer.
In aspect of GD, more controversies have existed depending on whether the study targets all patients with GD or specifically those who have undergone surgery for GD. Most of studies including thyroidectomy patients with GD represented increased risk of thyroid cancer; however, several studies including our study showed no difference in the occurrence of thyroid cancer based on the presence of GD. Studies on the impact of GD on the prognosis of thyroid cancer also show inconsistent results. In this time, we explore the overall trend of the association between AITD and thyroid cancer and to consider future necessary research