The evaluation of the mutated allele peak at the Sanger sequencing electropherogram relative to the wild-type allele peak showed that for 4 of 10 CRC-PDE with KRAS mutation, the mutated cells seemed to be positively selected over time; by week 4 of culture, there were 50% more mutated clones in the culture relative to day 0. The gene discussed is ALDH7A1; the disease is colorectal carcinoma.