KRAS and adenoma: First, KRAS mutation also occurs frequently in dysplastic aberrant crypt foci (microadenomas) and in some small tubular adenomas, suggesting that KRAS mutation may initiate a subset of small adenomas with limited potential for progression.6,7 Second, around 70% of CRCs lack mutation of KRAS. 8 From this it follows that most of the precancerous lesions that eventually become cancers do not in fact have KRAS mutation.