Family history and genetic syndromes

In short

A close relative with colorectal cancer or an advanced polyp raises your own risk and usually means starting screening earlier and using coloscopy specifically. A small number of inherited syndromes — Lynch syndrome and familial adenomatous polyposis are the most familiar — raise the risk much more, and require their own surveillance plan with genetic counselling. Most people with a positive family history do not have one of these syndromes, but it is the kind of question worth asking out loud.

What this page covers

How clinicians categorise family history when planning screening, what Lynch syndrome and familial adenomatous polyposis are and what they mean for relatives, when genetic counselling is reasonable, and what to ask your clinician. The numbers given are directional rather than precise; specific surveillance intervals are determined by the guideline body relevant to your country and by your clinician's reading of your situation.

What "first-degree relative" means and why it matters
Average risk, increased risk, and high risk — how the lines are drawn
Lynch syndrome, familial adenomatous polyposis, and other inherited conditions
When to consider genetic counselling, and what it involves
What to ask your clinician

Family history, in plain terms

A first-degree relative is a parent, sibling, or child. A second-degree relative is a grandparent, aunt, uncle, niece, nephew, half-sibling, or grandchild. Family history risk for colorectal cancer is calibrated mostly to first-degree relatives, with second-degree history adding context.

Two pieces of information matter when you talk to a clinician about family history. First, the relationship — which side of the family, how close. Second, the age at diagnosis — a colorectal cancer in a parent diagnosed in their forties is a different signal from one diagnosed in their eighties. If you can, gather these details before your appointment. A telephone call to a relative often produces more accurate information than a half-remembered conversation from years ago.

What also matters, but is often forgotten, is whether the family member had an advanced polyp — a polyp that was large, contained higher-grade changes, or had villous features on pathology. An advanced polyp in a first-degree relative is treated similarly to a colorectal cancer in screening planning. Cousins and ordinary polyps do not generally change average-risk planning. Aunts and uncles do, but to a lesser degree than parents and siblings.

How risk categories are drawn

Most guideline bodies sort patients into broad categories rather than calculate individual risk percentages. The categories below approximate how this is done in the United States, the United Kingdom, and across Europe, with consensus from the U.S. Multi-Society Task Force, the British Society of Gastroenterology, the American College of Gastroenterology, and the European Society of Gastrointestinal Endoscopy.

Category	Family history pattern	Typical screening approach
Average risk	No first-degree relative with colorectal cancer or advanced polyp; no inherited syndrome	Programme or guideline-defined screening, starting in mid-forties or fifties depending on country
Increased risk	One first-degree relative with colorectal cancer or advanced polyp at any age, or two second-degree relatives	Coloscopy as first-line, often starting earlier than the standard programme age, with a shorter interval than ten years
High risk (familial)	Multiple first-degree relatives, especially diagnosed young, or strong familial pattern without confirmed syndrome	Earlier coloscopy, shorter intervals, often a referral to a familial colorectal cancer clinic
High risk (genetic syndrome)	Confirmed Lynch syndrome, FAP, MUTYH-associated polyposis, or related condition	Surveillance schedule defined by the syndrome, with genetics input

The exact thresholds — at what age the family member must have been diagnosed for you to be moved to a higher-risk pathway, how much earlier you start, how often you are scoped — vary between guidelines and have shifted over recent years. The principle is steady: closer and younger is more concerning; distant and older is less so.

Lynch syndrome

Lynch syndrome (sometimes called hereditary nonpolyposis colorectal cancer, or HNPCC) is the most common inherited cause of colorectal cancer. It is caused by a fault in one of a small set of genes — most often MLH1, MSH2, MSH6, PMS2, or EPCAM — that normally repair errors in DNA. People with Lynch syndrome carry a substantially increased lifetime risk of colorectal cancer, and a raised risk of cancers of the endometrium (the lining of the uterus), the ovaries, the stomach, the small bowel, the urinary tract, and other organs.

Lynch syndrome is autosomal dominant: a parent with the gene change has a fifty-fifty chance of passing it to each child. Surveillance for confirmed Lynch syndrome typically involves coloscopy beginning in early adulthood with short intervals (often every one to two years), gynaecological surveillance for women, and discussion of risk-reducing options. The exact schedule depends on which gene is involved and on national guidelines from bodies such as the European Hereditary Tumour Group, the National Comprehensive Cancer Network, and the British Society of Gastroenterology.

Lynch syndrome is suspected when a family has multiple cancers across the spectrum above, particularly diagnosed young; when a tumour pathology report mentions microsatellite instability or mismatch repair deficiency; or when a relative has been diagnosed and confirmed. Many cancer centres now test all newly diagnosed colorectal and endometrial cancers for these features as a routine, which means relatives are sometimes the first to be told a syndrome runs in the family.

Familial adenomatous polyposis (FAP)

Familial adenomatous polyposis is a rarer condition caused by changes in the APC gene. People with classic FAP develop hundreds to thousands of polyps in the colon, usually beginning in the teenage years. Without surveillance and treatment, the lifetime risk of colorectal cancer approaches certainty by middle age.

An attenuated form of FAP (sometimes called AFAP) involves fewer polyps appearing later in life and has a less aggressive but still meaningfully raised risk. Both forms are autosomal dominant, with a fifty-fifty inheritance per child.

Surveillance for FAP begins in adolescence with periodic coloscopy or sigmoidoscopy, and for many patients leads to a planned removal of the colon (colectomy) once polyp burden becomes unmanageable. Surveillance also includes the upper gastrointestinal tract, the thyroid, and other sites where FAP-related tumours can occur. Care is usually coordinated by a specialist polyposis service.

Other inherited conditions

Several other inherited syndromes raise colorectal cancer risk and have their own surveillance pathways. None is common, and you should not try to diagnose yourself from this list. Mention any of these terms to your clinician if they appear in your family history.

MUTYH-associated polyposis (MAP) — recessively inherited, causing multiple adenomatous polyps and raised colorectal cancer risk
Peutz–Jeghers syndrome — characterised by hamartomatous polyps and characteristic pigmented spots, with raised gastrointestinal and other cancer risks
Juvenile polyposis syndrome — multiple juvenile polyps, with raised colorectal and gastric cancer risk
Serrated polyposis syndrome — multiple serrated polyps in the colon, with raised colorectal cancer risk
Cowden syndrome (PTEN hamartoma tumour syndrome) — multiple cancer risks including colorectal

When to consider genetic counselling

A referral to a clinical geneticist or genetic counsellor is reasonable when any of the following apply. The list is not exhaustive, and your local service may use slightly different referral criteria.

A first-degree relative diagnosed with colorectal cancer at a young age
Two or more first-degree relatives with colorectal cancer or advanced polyps
A pattern of related cancers in the family — colorectal, endometrial, ovarian, gastric, urothelial, small bowel — particularly diagnosed young
A relative whose tumour was reported to have microsatellite instability or mismatch repair deficiency
A known gene change in the family
You have personally had multiple polyps, or a colorectal cancer at a young age
An Ashkenazi Jewish heritage and a family history of related cancers (some founder variants are more common in this population)

A counselling visit usually involves drawing a detailed family pedigree, reviewing any pathology reports available, discussing what testing might or might not show, and explaining the implications for you and for relatives if a result is positive. Testing is not always recommended — sometimes a careful pedigree gives all the information needed to plan surveillance, and a negative test would not change the plan. Counselling also covers what a negative test means in a family without a known gene change, which is often less reassuring than people assume.

What changes for screening if your family history is significant

For most people with a single first-degree relative diagnosed at typical screening ages, the change is modest: coloscopy as the first-line test, often starting earlier than the standard programme age, and a shorter interval if no polyps are found. For those with stronger family patterns, screening is moved to a familial colorectal cancer clinic that follows a specific protocol. For those with confirmed inherited syndromes, surveillance is intense and lifelong, and is typically coordinated through a specialist service.

If you are scheduling a coloscopy and you have not had a chance to discuss your family history in detail, it is reasonable to raise it with the booking clinician or at the pre-procedure appointment. Family history can change whether the test is categorised as screening or diagnostic, which has practical consequences for billing in the United States and for surveillance scheduling everywhere.

What to ask your clinician

Given my family history as I have described it, am I average risk, increased risk, or high risk?
What age should I start screening, and what test do you recommend first?
How often should I be screened if my coloscopy is normal?
Should I see a genetic counsellor, and if so, where is the nearest service?
Should my siblings or my children be screened earlier because of my history?
If a relative had a tumour tested for Lynch features, can I see the report?
What records of family pathology would help you advise me better?
If I am considered higher risk, is there a familial colorectal cancer clinic I should be referred to?

Common worries, briefly addressed

My grandfather had colon cancer in his eighties — does that change anything?

Probably not very much. A second-degree relative diagnosed at typical screening ages is consistent with average-risk screening for you. Mention it anyway when planning, but do not expect it to change your starting age.

My mother had a polyp removed — should I start earlier?

It depends on what the polyp was. An ordinary small adenoma in a parent does not generally trigger earlier screening. An advanced adenoma — large, with high-grade changes, or with villous features — is treated similarly to a small cancer for the purposes of family planning. Ask whether the pathology report can be retrieved.

I am adopted and do not know my family history.

This is more common than people assume, and clinicians are used to it. The default is average-risk screening unless you have personal symptoms or findings that suggest otherwise. If your own coloscopy reveals features that raise suspicion of a syndrome, that is when genetics may be considered for you specifically.

If I get tested, will it affect my insurance?

Laws vary. In the United States, the Genetic Information Nondiscrimination Act protects against the use of genetic information by health insurers and employers but does not cover life, disability, or long-term care insurance. In the United Kingdom, a moratorium agreement covers most life insurance situations within stated limits. Ask the genetic counsellor about the rules where you live before testing, not afterwards.

I tested negative — am I in the clear?

Not always. A negative test in a family with a known gene change is genuinely reassuring, and may move you back to average-risk screening. A negative test in a family without a known gene change is harder to interpret, because the syndrome may be present but undetected by current testing. Your genetic counsellor will explain which kind of negative your result is.

Sources

U.S. Multi-Society Task Force on Colorectal Cancer — recommendations on screening for individuals with a family history
American College of Gastroenterology — clinical guideline on hereditary colorectal cancer syndromes
National Comprehensive Cancer Network — guidelines on genetic/familial high-risk assessment for colorectal cancer
British Society of Gastroenterology — guidance on hereditary colorectal cancer and surveillance
European Society of Gastrointestinal Endoscopy — performance measures and guidance on surveillance
European Hereditary Tumour Group — recommendations for Lynch syndrome and polyposis syndromes
National Institute for Health and Care Excellence — guidance on molecular testing and management
National Society of Genetic Counselors — practice guidance on cancer risk counselling