BRAF and thyroid gland follicular carcinoma: Since RAS is involved in the evolutionary processes from benign FA to low-grade malignant NIFTP and even more malignant follicular carcinoma,[39] RAS mutation rate is essential for clinical diagnosis, especially for the samples which cannot be determined cytologically.[40] In the present study, RAS mutation comprised 17.4% of the Bethesda III/IV/V samples, making it the second most common mutation type after BRAF (Table 3).