Considering the complete set of PTEN mutations, the AF of PTEN mutations is lower than that of APC or TP53 mutations, in agreement with the current view that alterations in PTEN are a later event in CRC carcinogenesis22; however, AFs are similar to those of KRAS, and higher than those of PIK3CA, suggesting selection. This evidence concerns the gene KRAS and colorectal carcinoma.