RASSF1 and metastatic malignant neoplasm in the lymph nodes: Among these five genes, DACT2 methylation is associated with gender, age, and tumor size (all P < 0.05), HIN1 methylation is associated with tumor size (P < 0.05) and extra-thyroidal extension (P < 0.01), RASSF1A methylation is associated with lymph node metastasis (P < 0.01).