Early-onset colorectal cancer: A separate subset of colorectal cancer

Table 1 Main pathways involved in the onset and development of colorectal cancer

	Chromosomal instability or “suppressor” pathway	Microsatellite instability or “mutator” pathway	CpG island methylator phenotype or “serrated” pathway
Percentage of CRC	80%-85%	10%-15%	40%
Clinical characteristics	Predominant location of tumor in the distal colon	Predominant location of tumor in the right colon	Predominant location of tumor in the right colon
		Better prognosis	Female sex
Histopathologic characteristics	No lymphocytic reactions	Lymphocytic reactions	Low-grade tumor differentiation
	No mucinous features	Mucinous features
	Good differentiation	Signet ring cells
		Low-grade tumor differentiation
Molecular characteristics	Aneuploidy, polyploidy, loss of heterozygosity	Diploidy, MSI	Methylation of CpG islands
Main genes involved	APC, P53, KRAS, C-MYC, DCC/SMAD4, TGFBR, PIK3CA	MLH1, MSH2,	BRAF, MSI
		MSH6, PMS2,
		TGF-βRII, IGFIIR,
		MSH3 and BAX
Hereditary syndromes	Familial adenomatous polyposis	Lynch syndrome

CRC: Colorectal cancer; MSI: Microsatellite instability.