KRAS and adenoma: It has been described that the ratio KRAS-4A/KRAS-4B is significantly reduced in 6 CRC cell lines when compared with cells derived from normal colon and in tumour from 4/9 patients with sporadic CRC when compared with the adjacent normal mucosa [9] and similar results were obtained in adenomas of mouse small intestine in the absence of KRAS -activating mutations [15].