Table 2.

Molecular testing strategies in hereditary colorectal cancer (CRC)

Risk category	Somatic or constitutive testing	Eligibility	Test
Family history of CRC	Somatic	Moderate-risk or high-risk family history	dMMR/pMMR
	Constitutive	Amsterdam criteria112 families where MMR testing is not possible	Panel testing of affected individuals or unaffected testing
CRC	Somatic	Universal testing	dMMR/pMMR and subsequent testing as defined by NICE DG27 guideline5 7 8 18 112
Early onset CRC (EOCRC)	Constitutive	Diagnosis of CRC at 30 years and under	Panel testing determined by MMR status
Lynch-like syndrome	Somatic	dMMR tumours without hypermethylation/BRAF pathogenic variant and no constitutional pathogenic variant in MMR genes	Somatic testing panel
Serrated polyposis syndrome	Constitutive/ somatic	Diagnosis of exclusion	Exclude known predisposition syndromes
Multiple colorectal adenoma (MCRAs)	Constitutive	MCRAs under 60 years of age with ≥10 adenomas, or patients over 60 years of age with ≥20 adenomas, or ≥10 with a family history of multiple adenomas or CRC	Gene panel testing

dMMR, MMR proficient; MMR, mismatch repair; NICE, National Institute for Health and Care Excellence; pMMR, MMR deficient.