SLC5A5 and thyroid cancer: Therefore, according to the mentioned challenges, this study seeks to investigate the methylation degree of a large region of NIS promoter in a set of multinodular goiters (MNG) samples (as the benign samples), malignant thyroid tumors including PTC and FTC, and their surrounding non-tumor tissue samples to suggest a methylation region as a discriminatory biomarker for early diagnosis of thyroid nodules.