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Lynch syndrome (MSH2)
When caused by variants in MSH2, Lynch syndrome typically raises lifetime colorectal cancer risk to 40-80% and endometrial cancer risk to 25-60%. Early and regular surveillance through NHS pathways can detect cancers at curable stages, whilst risk-reducing options may be appropriate for some individuals.
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Overview
Lynch syndrome represents the most common inherited cause of colorectal cancer, accounting for approximately 3% of all colorectal cancer diagnoses in the United Kingdom. The condition arises when someone inherits a pathogenic variant in one of several genes responsible for repairing errors that naturally occur during DNA copying. When MSH2 specifically carries a disease-causing change, affected individuals face substantially elevated risks for multiple cancer types throughout their lifetime, with colorectal and endometrial cancers being most frequent. Research suggests that around 1 in 440 people in the general population carry a Lynch syndrome-associated variant, though many remain undiagnosed until cancer develops [PMID:28632866].
The condition follows an autosomal dominant inheritance pattern, meaning a single altered copy of MSH2 is sufficient to increase cancer susceptibility. However, having the genetic predisposition does not guarantee cancer will develop - penetrance varies considerably between individuals and depends partly on which specific gene is affected. Unlike some hereditary cancer syndromes, Lynch syndrome does not typically cause physical features or developmental concerns outside the increased cancer risk. Recognition of the condition has grown considerably since molecular testing became widely available in the 1990s, allowing at-risk family members to access tailored surveillance before symptoms appear.
Management through the NHS Genomic Medicine Service focuses on early cancer detection rather than prevention in most cases. Regular colonoscopy surveillance, beginning substantially earlier than population screening programmes, can identify precancerous changes or early-stage tumours when treatment outcomes are most favourable. For endometrial cancer risk, surveillance options and risk-reducing surgery may be discussed with affected individuals once childbearing is complete. The identification of Lynch syndrome in one family member creates opportunities for predictive testing in relatives, potentially preventing cancer deaths through timely intervention.
Symptoms & clinical features
Lynch syndrome itself produces no symptoms - it is a genetic predisposition rather than a disease with clinical features. The condition becomes apparent only when associated cancers develop, typically at younger ages than seen in the general population. Colorectal cancers in people with Lynch syndrome often emerge between ages 40-50, compared to average onset around age 70 in those without hereditary risk factors. These tumours may present with rectal bleeding, persistent changes in bowel habits, abdominal pain or unexplained weight loss, though many are detected through surveillance colonoscopy before symptoms arise [PMID:31704009].
Endometrial cancer, the second most common malignancy in Lynch syndrome, usually manifests through abnormal vaginal bleeding - particularly bleeding after menopause or between menstrual periods. Some individuals experience pelvic pain or pressure, though early-stage disease frequently causes no noticeable symptoms. Beyond these two primary cancer types, Lynch syndrome elevates risk for gastric, ovarian, small bowel, hepatobiliary, urinary tract, brain and sebaceous skin tumours. Each may present with symptoms specific to the affected organ system. The development of multiple primary cancers over a lifetime, or colorectal cancer diagnosed before age 50, often prompts genetic evaluation even when family history appears limited.
Some people with MSH2 variants develop multiple sebaceous skin lesions - yellowish bumps typically appearing on the face and trunk. Whilst these benign growths rarely cause medical problems, their presence alongside colorectal polyps or cancer strengthens suspicion for Lynch syndrome. the absence of cancer does not exclude the diagnosis - many individuals carry pathogenic MSH2 variants throughout life without developing malignancy, highlighting the incomplete penetrance characteristic of this condition.
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Affected organs
The gastrointestinal tract bears the highest cancer burden in Lynch syndrome, with the colon and rectum most frequently affected. Colorectal tumours in this population often develop in the proximal colon (right side), contrasting with the distal distribution more typical of sporadic cases. The small intestine, stomach and hepatobiliary system (liver, bile ducts, gallbladder and pancreas) also face elevated malignancy risk, though absolute rates remain lower than for colorectal sites. Gastric cancer risk appears particularly increased in certain populations, with some studies indicating lifetime risks approaching 10% in MSH2 variant carriers [PMID:23362271].
In individuals with a uterus, the endometrium represents a major site of cancer development. Lifetime endometrial cancer risk for those with MSH2 variants ranges from approximately 25% to 60% depending on the study population examined, making this the most common extracolonic manifestation in female carriers. The ovaries also show increased cancer susceptibility, with lifetime risks estimated between 10-15%. Urinary tract malignancies - including cancers of the kidney, ureter and bladder - occur more frequently than in the general population. The central nervous system may develop glioblastomas or other brain tumours, whilst the skin can produce sebaceous adenomas, sebaceous carcinomas and keratoacanthomas. This multi-organ cancer spectrum necessitates comprehensive surveillance strategies rather than single-site monitoring.
Risks & severity
The cancer risks associated with MSH2 pathogenic variants are substantial but variable between individuals. Evidence suggests lifetime colorectal cancer risk ranges from 40% to 80%, meaning that even in the most conservative estimates, nearly half of variant carriers will develop bowel cancer if they live a normal lifespan without surveillance. For endometrial cancer, lifetime risk estimates span 25-60%, with most studies clustering around 40-50%. These figures far exceed general population risks of approximately 5% for colorectal cancer and 3% for endometrial cancer [PMID:28632866].
Age of onset represents a critical consideration in Lynch syndrome management. Colorectal cancers typically emerge one to two decades earlier than sporadic cases, with median diagnosis occurring in the fifth decade of life. However, tumours can develop in the twenties or thirties, necessitating surveillance initiation by age 25 or earlier if family history suggests particularly early onset. Endometrial cancers similarly arise at younger ages than average, though most occur after age 40. The risk of developing a second primary cancer remains elevated throughout life - individuals who have had one Lynch syndrome-associated malignancy face continuing high risk for additional tumours in different organs.
Severity varies considerably depending on whether cancer is detected through surveillance or symptomatically. Colonoscopy programmes can identify colorectal cancers at early stages when surgical cure rates exceed 90%, fundamentally altering prognosis compared to later-stage diagnosis. The accelerated progression from polyp to cancer in Lynch syndrome - potentially occurring within 2-3 years rather than the typical 10-year timeframe - underscores the importance of frequent surveillance intervals. Survival outcomes for Lynch syndrome-associated cancers generally match or exceed those for sporadic tumours when stage at diagnosis is equivalent, suggesting that the genetic background itself does not worsen prognosis beyond increasing cancer occurrence.
Genetic causes
MSH2 encodes a protein that functions as part of the DNA mismatch repair system, a cellular quality-control mechanism responsible for identifying and correcting errors introduced during DNA replication. Each time a cell divides, its entire genome must be copied, a process that occasionally introduces mismatched base pairs - adenine paired with cytosine rather than thymine, for example. The MSH2 protein partners with MSH6 to form a complex called MutSα, which scans newly replicated DNA for these mismatches and recruits additional repair machinery to excise and replace the incorrect sequence [PMID:11733589].
When someone inherits a pathogenic variant in MSH2, cells throughout their body contain one functional copy and one non-functional copy of the gene. Initially, the remaining normal copy provides sufficient mismatch repair capacity to maintain genomic stability. However, if the functional copy becomes inactivated in a particular cell - through mutation, deletion or other mechanisms - that cell loses effective mismatch repair capability entirely. Replication errors begin accumulating uncorrected, particularly in repetitive DNA sequences called microsatellites. This phenomenon, termed microsatellite instability, accelerates mutation accumulation across the genome, including in genes that normally suppress tumour formation or regulate cell growth [PMID:31704009].
The spectrum of pathogenic MSH2 variants includes nonsense mutations that introduce premature stop signals, frameshift deletions or insertions that disrupt the protein-coding sequence, splice site changes that prevent correct RNA processing, and missense substitutions that impair protein function. Large deletions removing part or all of the MSH2 gene also occur. Notably, deletions extending into the neighbouring EPCAM gene can cause Lynch syndrome through an indirect mechanism - loss of EPCAM leads to epigenetic silencing of MSH2 in certain tissues, producing a similar phenotype despite the MSH2 coding sequence remaining intact. Pathogenic variants are scattered throughout the gene rather than clustering in specific regions, requiring comprehensive sequencing for diagnostic purposes.
- MSH2 mutS homolog 2The MSH2 gene provides instructions for a protein that is essential for DNA mismatch repair, a critical process for maintaining genomic stability and preventing cancer.
Inheritance pattern
Lynch syndrome caused by MSH2 variants follows an autosomal dominant pattern of inheritance. This means that inheriting a single altered copy of the gene from either parent is sufficient to substantially increase cancer risk, whilst inheriting two normal copies results in population-level risk. Each child of someone with a pathogenic MSH2 variant has a 50% chance of inheriting that variant and therefore the associated cancer predisposition. The condition affects males and females equally, though cancer risks for specific tumour types differ by sex - endometrial and ovarian cancers obviously affect only those with the relevant anatomy.
It is important to recognise that inheriting the genetic change does not mean cancer is inevitable. Penetrance - the proportion of variant carriers who actually develop cancer during their lifetime - is incomplete, meaning some individuals carry pathogenic MSH2 changes throughout life without malignancy emerging. Environmental factors, chance events and possibly genetic modifiers influence whether and when cancer develops. Family history may appear limited in some cases if by chance the variant has been transmitted through individuals who did not develop cancer, or if cancers occurred but were attributed to other causes before genetic testing became available.
When Lynch syndrome is identified in one family member, genetic counselling is typically offered to at-risk relatives. Predictive testing can determine whether relatives have inherited the familial variant, allowing those who test negative to discontinue intensive surveillance whilst those who test positive can access appropriate screening. Children are generally not offered predictive testing until they approach the age when surveillance would commence, typically late teenage years or early twenties, as the result provides no actionable information in childhood and they should have the opportunity to make an autonomous decision about testing when developmentally appropriate.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis of Lynch syndrome typically begins with recognition of clinical features suggesting hereditary colorectal cancer - early onset disease, multiple affected family members across generations, or the development of Lynch syndrome-associated tumours. The NHS Genomic Medicine Service recommends that all colorectal cancers diagnosed before age 50, and all endometrial cancers regardless of age, undergo tumour testing for mismatch repair deficiency. This initial screening usually employs immunohistochemistry to assess expression of mismatch repair proteins (MLH1, MSH2, MSH6, PMS2) in tumour tissue, or molecular testing to detect microsatellite instability [PMID:33711273].
When tumour screening suggests mismatch repair deficiency - typically shown by absent staining for MSH2 and MSH6 proteins - germline genetic testing is offered to determine whether the individual carries an inherited pathogenic variant. Blood or saliva samples provide DNA for sequencing of the MSH2 gene and analysis for deletions or duplications. In approximately 10-15% of cases, the mismatch repair deficiency results from somatic (acquired) changes in the tumour rather than an inherited predisposition, so germline testing may return negative despite abnormal tumour findings. Testing for EPCAM deletions may be included given their ability to silence MSH2 expression. NHS genetic testing for Lynch syndrome is available through the Genomic Medicine Service under test code R207 (Inherited colorectal cancer and polyposis) for those meeting clinical criteria. Referral typically comes from oncology, gastroenterology or genetic services, though increasingly colorectal and gynaecological surgeons initiate the pathway when tumour screening suggests hereditary disease. Genetic counselling forms an integral part of the testing process, ensuring individuals understand the implications for themselves and family members before proceeding.
Management & lifestyle
Management of Lynch syndrome centres on intensive surveillance to detect cancers at early, curable stages rather than preventing tumour development entirely. For individuals with MSH2 variants, NHS guidelines recommend colonoscopy every two years beginning at age 25, or five years younger than the earliest colorectal cancer in the family if that occurred before age 25. This frequent interval reflects evidence that colorectal cancers can develop rapidly in Lynch syndrome, potentially progressing from small polyp to invasive malignancy within 2-3 years. Any polyps identified during surveillance are removed, interrupting the pathway to cancer [PMID:31704009].
For those with a uterus, annual endometrial sampling and transvaginal ultrasound from age 35 may be offered, though evidence for the effectiveness of endometrial surveillance remains less robust than for colonoscopy. Risk-reducing hysterectomy and bilateral salpingo-oophorectomy (removal of uterus, fallopian tubes and ovaries) can be considered once childbearing is complete, typically reducing endometrial cancer risk by over 95% and ovarian cancer risk substantially. This surgical approach requires careful discussion of the benefits, risks and quality-of-life implications, including premature menopause if performed before natural menopause would occur. Upper gastrointestinal endoscopy every 2-3 years from age 40-45 may be recommended, particularly in families with gastric cancer history, though evidence supporting this intervention is more limited.
Lifestyle modifications may modestly influence cancer risk, though their impact in Lynch syndrome specifically remains uncertain. Some studies suggest that regular aspirin use might reduce colorectal cancer incidence in mismatch repair variant carriers, though optimal dosing and duration are not firmly established - any aspirin regimen should be discussed with a clinician given bleeding risks [PMID:28555348]. Maintaining healthy body weight, engaging in regular physical activity and limiting alcohol consumption represent sensible measures consistent with general cancer prevention advice, though they cannot substitute for surveillance. Smoking cessation is particularly important given its broad cancer-promoting effects. Genetic counselling remains available throughout life to discuss evolving evidence, family planning implications and testing options for relatives.
UK care pathway
Individuals with Lynch syndrome in the United Kingdom access specialist care through the NHS Genomic Medicine Service, which coordinates genetic testing, clinical surveillance and family cascade screening. Initial referral typically occurs through oncology or gastroenterology when tumour characteristics suggest hereditary disease, or through primary care when family history raises concern. Clinical genetics departments provide genetic counselling before and after testing, explaining inheritance patterns, cancer risks and surveillance options. Testing is commissioned under test directory code R207 (Inherited colorectal cancer and polyposis) for those meeting eligibility criteria, which include early-onset colorectal or endometrial cancer, multiple Lynch syndrome-associated tumours, or family history consistent with dominant inheritance.
Once a diagnosis is confirmed, ongoing surveillance is usually coordinated through local gastroenterology services for colonoscopy and gynaecology for endometrial monitoring where appropriate. Some centres operate dedicated hereditary cancer clinics bringing together relevant specialties. PanelApp panels such as "Inherited colorectal cancer and polyposis" guide which genes are analysed during testing. Genetic counsellors support family communication, helping affected individuals share information with relatives who may benefit from predictive testing. The NHS also provides access to psychological support services for those finding their diagnosis distressing or struggling with cancer anxiety. Research participation opportunities may be offered through clinical genetics departments, contributing to evolving understanding of optimal management strategies.
Frequently asked questions
If I have Lynch syndrome, does that mean I will definitely get cancer?
No, having a pathogenic MSH2 variant substantially increases cancer risk but does not guarantee cancer will develop. Studies suggest 40-80% of MSH2 variant carriers develop colorectal cancer during their lifetime, meaning 20-60% do not. Regular surveillance allows early detection when cancer does occur, significantly improving treatment outcomes.
How often do I need colonoscopy if I have Lynch syndrome?
NHS guidelines typically recommend colonoscopy every two years starting at age 25 for individuals with MSH2 variants, or five years before the youngest family cancer diagnosis if earlier. This frequent schedule reflects evidence that colorectal cancers can develop quickly in Lynch syndrome, potentially within 2-3 years from small polyps.
Should my children be tested for Lynch syndrome?
Genetic testing for children is usually deferred until late teenage years or early twenties when surveillance would begin, unless there are exceptional circumstances. This allows young people to participate in the testing decision themselves. Each child has a 50% chance of inheriting the familial variant, and knowing their status allows personalised cancer screening if positive or discontinuation of intensive surveillance if negative.
Can I do anything to lower my cancer risk besides surveillance?
Some research suggests regular aspirin use might reduce colorectal cancer risk in Lynch syndrome, though optimal dosing remains uncertain and aspirin carries bleeding risks - discuss this with your clinical team before starting. Maintaining healthy weight, exercising regularly and avoiding smoking represent sensible general measures, though surveillance remains the cornerstone of risk management.
Will having Lynch syndrome affect my life insurance or mortgage applications?
UK law prohibits most genetic discrimination, but life insurance companies may ask about genetic test results for policies over £500,000 and insurers can consider family history of cancer. The Concordat and Moratorium on Genetics and Insurance provides some protection. Genetic counsellors can discuss these implications before testing, and some people choose to arrange insurance before pursuing genetic diagnosis if their cancer risk is already apparent from family history.