Some colorectal cancers in LS can in fact grow out from MMR-proficient adenomas after secondary inactivation of the MMR system; however, a larger portion of cancers appears to develop from mismatch repair deficient crypt focus (MMR-DCF), either through an adenomatous phase or as nonpolypous lesions with immediate invasive growth [23]. This evidence concerns the gene MRC1 and colorectal cancer.