KRAS and follicular thyroid adenoma: For surgical specimens, after excluding one case of WDT-UMP with RAS-positive mutation, K-RAS mutations were detected in 4 out of the 12 (33.3%) malignant nodules (1 PTC and 3 FTCs) and in 6 out of 29 (20.7%) benign nodules, including 1 follicular adenoma, 1 hurthle cell adenoma, and 4 hyperplastic nodules.