After the initial report by Li et al that 1 out of 22 sporadic colon adenocarcinomas (4.5%) harboured the amino acid substitution altering Lys-1423 in the NF1 GRD [133], loss of heterozygosity (LOH) involving the NF1 gene in 14-57% of colorectal carcinomas was reported in two small studies [134, 135]. This evidence concerns the gene NF1 and colon adenocarcinoma.