The first 60 days: Lynch syndrome-associated colorectal cancer

Lynch syndrome-associated bowel cancer is bowel cancer in someone born with a fault in one of the genes that proofread DNA copying errors. The tumours tend to arise younger and on the right side, they carry the mismatch repair defect that makes immunotherapy work, and the diagnosis changes the care of the whole family as well as the care of the patient. Below, week by week, is what OnCo's record of Lynch syndrome-associated colorectal cancer says about the first two months: the order is typical, the timing is yours to ask about. Sections appear only where the record has something to say. Orientation, not medical advice.

Weeks 1 to 2

What happens now

Staging tests establish exactly what and where the cancer is. Everything else follows from the answers.

Biomarkers your report may list

Mismatch repair protein loss on immunohistochemistry, or microsatellite instability, on every colorectal cancer at diagnosis MLH1 promoter methylation and BRAF V600E testing to separate sporadic from inherited mismatch repair loss Germline testing of MLH1, MSH2, MSH6, PMS2 and EPCAM to confirm the diagnosis and to test relatives

Ask which of these were tested and what the results were; see the report reader for what each value means.

Tests and imaging linked to this cancer

Germline (hereditary) testing Histopathology & immunohistochemistry MSI and mismatch-repair testing

Weeks 1 to 3

Who is on your team

These specialties appear in the standard of care for this cancer. In most centres they meet weekly as a tumour board to agree each plan; you can ask when yours was discussed and what was decided.

A second opinion from a centre that treats many similar cases is normal, not rude; the standard of care tells you what to compare it against.

Weeks 2 to 6

Decisions coming up

Each row is a setting from the standard of care, in the order it usually arises. Not all will apply to you; your stage and biomarkers decide which do. The guideline grade, where recorded, says how strong the evidence is.

1.Finding the syndrome NICE NG151: colorectal cancer (published January 2020, last updated December 2021, last reviewed April 2026)
Mismatch repair immunohistochemistry or microsatellite instability testing on every colorectal cancer; MLH1 promoter methylation testing where MLH1 is lost, because most of those cancers are sporadic; germline testing when methylation is absent, then cascade testing of relatives.
MSI and mismatch-repair testing Histopathology & immunohistochemistry Germline (hereditary) testing Lynch syndrome MLH1 promoter methylation (sporadic versus Lynch mismatch repair loss)
2.Risk reduction in carriers NICE NG151: colorectal cancer (published January 2020, last updated December 2021, last reviewed April 2026)
Consider daily aspirin for more than two years (NICE NG151 1.1.1, from CAPP2); colonoscopic surveillance at intervals set by gene and age; discussion of the extent of colectomy when a cancer is found; gynaecological risk-reducing surgery after childbearing for women.
Aspirin for cancer prevention and adjuvant therapy Colonoscopy Surveillance intervals after polypectomy Colectomy Chemoprevention & risk-reducing surgery

Every visit

Questions to ask at each visit

Generated from this cancer's standard of care, biomarkers and open problems. Take the group that matches where you are. To tick, add your own and print, open the one-page appointment sheet.

Newly diagnosed

What is my exact diagnosis, stage, and grade, and which tests established them?Everything else follows from an accurate stage and subtype.
Which biomarkers have been tested on my tumour (for example Mismatch repair protein loss on immunohistochemistry, or microsatellite instability, on every colorectal cancer at diagnosis, MLH1 promoter methylation and BRAF V600E testing to separate sporadic from inherited mismatch repair loss, Germline testing of MLH1, MSH2, MSH6, PMS2 and EPCAM to confirm the diagnosis and to test relatives), and what were the results?These results decide eligibility for targeted therapy, immunotherapy, and trials.
Which subtype is my cancer, and does that change the recommended treatment?Recognised subtypes for this cancer include MLH1-associated Lynch syndrome, MSH2-associated Lynch syndrome, including EPCAM deletions, MSH6-associated Lynch syndrome.
Is germline (inherited) genetic testing recommended for me or my family?Inherited variants can change treatment and matter for relatives.

Finding the syndrome

For my situation (finding the syndrome), which of the standard options do you recommend and why?Guideline options include: Mismatch repair immunohistochemistry or microsatellite instability testing on every colorectal cancer; MLH1 promoter methylation testing where MLH1 is lost, because most of those cancers are sporadic; germline testing when methylation is absent, then cascade testing of relatives.

Risk reduction in carriers

For my situation (risk reduction in carriers), which of the standard options do you recommend and why?Guideline options include: Consider daily aspirin for more than two years (NICE NG151 1.1.1, from CAPP2); colonoscopic surveillance at intervals set by gene and age; discussion of the extent of colectomy when a cancer is found; gynaecological risk-reducing surgery after childbearing for women.

Any stage

Would a second opinion at a high-volume centre change anything, and can you help arrange it?Rare or high-stakes decisions benefit from a centre that treats many similar patients.
What supportive care (symptom control, nutrition, exercise, mental health, financial help) is available from the start?Supportive care improves quality of life and helps patients complete treatment.

From day one

Help that costs nothing

Much of what helps in the first weeks is free if you know to ask: testing, helplines, rides and lodging, second opinions, trial travel.

Any time

What to read next

Words this page and the cancer page use

Colonoscopy: Examining the whole large bowel with a flexible camera; polyps found on the way are removed (polypectomy), which prevents most bowel cancers.
Surveillance intervals after polypectomy: After polyps are removed, the date of your next colonoscopy is set by what was found, not by habit.
Serrated pathway: The serrated pathway is the second route to bowel cancer, running not through the familiar mushroom-shaped polyp but through flat, pale, saw-toothed lesions that are easy to miss at colonoscopy and rarely bleed.
MLH1 promoter methylation (sporadic versus Lynch mismatch repair loss): When a tumour has lost the MLH1 mismatch-repair protein, a methylation test on the tumour tells the two causes apart: methylation switching the gene off means a sporadic cancer, no methylation means an inherited Lynch syndrome mutation is likely and the whole family needs testing.
Colectomy: Removing the part of the colon containing the cancer along with its blood supply and lymph nodes, then joining the ends.
Lynch syndrome: Lynch syndrome is the most common inherited cancer syndrome: a faulty mismatch-repair gene raises lifetime bowel cancer risk to 40-80% and also endometrial and other cancers.
Germline vs somatic mutations: Germline mutations are inherited and in every cell; somatic mutations arise in the tumour only.
Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR): Microsatellite instability is the mark of a broken DNA spell-checker (loss of MLH1, MSH2, MSH6 or PMS2) that leaves thousands of mutations, so the tumour displays abnormal proteins that T cells can recognise.

Every term links to the glossary.