RASSF1 and thyroid nodule: Using these five genes, CALCA, RAR-beta, DAPK1, TIMP3, and RASSF1A for differential diagnosis of thyroid nodules with appropriate cut-off values, we were able to identify positive gene methylation in 33.33-88.10% of malignant nodules, but the diagnostic specificities were all low, ranging from 75.68 to 83.78%.