Table 1.

Colorectal cancer molecular subcategorization [23].

CRC type	Subcategory	Characteristics	Prevalence
Microsatellite instability	MSI-H: >30% of marker loci with instability (Bethesda panel of 5 markers or alternate panel) OR lack of MMR protein on IHC	Germline: MLH1, MSH2, MSH6, PMS2 Sporadic: Hypermethylation MLH1 Hypermutation profile but stable karyotype; strong correlation with BRAF mutations (40–45%) Right-sided lesions with poor diff, mucinous features and lymphocytic invasion Associated with CpG-Island methylation phenotype-high (CIMP-H)	5% 10%
Chromosomal instability	Includes both MSI-L (<30% of marker loci with instability) and MSS (No evidence instability) tumors:	Unstable karyotype, demonstrates chromosome gains and losses KRAS, TP53, APC, PIK3CA, SMAD4, CTNNB1 mutations More commonly associated with CIMP-low or negative	80–85%

MSI = microsatellite instability, MMR = mismatch repair, IHC = immunohistochemistry, MSS = microsatellite stable.