Mutations in the RAS family of oncogenes (NRAS, HRAS, and KRAS) are key molecular events in follicular-patterned neoplasms including follicular adenoma (FA, 20–25%), follicular thyroid carcinoma (FTC, 30–45%), and follicular variant of PTC (FVPTC, 30–45%), as well as high-grade tumors such as poorly differentiated thyroid carcinoma (20–40%) and anaplastic thyroid carcinoma (ATC, 20–30%) [27]. This evidence concerns the gene HRAS and thyroid gland undifferentiated (anaplastic) carcinoma.