RAF1 and thyroid gland carcinoma: Activation of the RAS–RAF–MEK cascade is not limited to thyroid cancers histologically characterised as PTCs, as activating mutations in RAS genes (particularly N-RAS) occur in 20–30% of follicular thyroid cancers (FTCs) as well as in a smaller percentage of potentially premalignant follicular adenomas (Vasko et al, 2003).