As a key component of the transforming growth factor beta (TGFB) pathway, which regulates the expression of thyroid-specific genes, tumor suppressor SMAD4 is crucial for thyroid development and function. SMAD4 gene promoter mutations have been identified in various cancers, including thyroid cancer. The aim of this study is to investigate the frequency and clinical significance of SMAD4 gene promoter mutations in patients with thyroid cancer. The study has encompassed 36 patients whose endometrial cancer tissue was analyzed for SMAD4 gene promoter mutations. The results of this study will provide valuable insights into the molecular mechanisms underlying thyroid cancer development and progression.