Figure 3: CRC classification in molecular subgroups. (a) Five molecular colorectal cancer subgroups have been proposed, stratified on the basis of genomic instability, presence/absence of CIMP [10]. The approximate frequencies of each CRC subtype in the Western population are illustrated. (b) Because the currently used criteria for CIN analysis are not uniform, as compared to MSI and CIMP, a classification into only 4 molecular subtypes has been proposed [77, 78]. The approximate frequencies in the Western population are illustrated. The distribution of the CIMP subgroup appears to correlate with ethnic differences (see text), suggesting that predisposition to the CIMP pathway may be tied to the contribution of yet unknown gene-environment interactions. MSI, microsatellite instability; CIMP, CpG Island methylator phenotype; CIN, chromosomal instability; CIMPL, CIMP Low.