What is Lynch syndrome?
Lynch syndrome is a type of inherited cancer syndrome associated with a genetic predisposition to different cancer types. This means people with Lynch syndrome have a higher risk of certain types of cancer. Lynch syndrome is also known as hereditary non-polyposis colorectal cancer (HNPCC).
Cancer begins when normal cells begin to change and grow out of control, forming a mass called a tumor. A tumor can be benign (non-cancerous) or malignant (cancerous), which means it can spread to other parts of the body. A benign tumor means the tumor can grow but will not spread.
People who have Lynch syndrome have a significantly increased risk of developing colorectal cancer. There is also an increased risk of developing other types of cancers, such as endometrial (uterine), gastric (stomach), ovarian, small bowel (small intestines), pancreatic, prostate, urinary tract, bile duct, sarcomas, and brain cancers, as well as sebaceous tumors of the skin.
Lynch syndrome is among the most common hereditary cancer syndromes. Estimates suggest as many as 1 in every 300 people may be carriers of a change, also called an alteration or mutation, in a gene associated with Lynch syndrome. Clues to whether there is Lynch syndrome in a family include diagnoses of colorectal, endometrial, ovarian, and/or other cancers in multiple relatives on the same side of a family. In addition, cancers associated with Lynch syndrome are more likely to be diagnosed at a young age. People with Lynch syndrome are at an increased risk of developing multiple types of cancers during their lifetime.
Cancers associated with Lynch syndrome frequently have a specific pattern of mutations known as microsatellite instability (MSI), also known as mismatch repair deficiency (MMR-D). ASCO recommends that tumor testing for Lynch syndrome be performed in all people diagnosed with colorectal cancer to look for MSI or MMR-D, and other recent guidelines recommend tumor testing for all endometrial cancers as well. (To learn about different types of genetic tests, listen to this podcast.)
What are signs of Lynch syndrome?
A set of criteria, called the revised Bethesda guidelines, is sometimes used to help doctors decide who should be tested for Lynch syndrome:
Developing colorectal cancer or endometrial cancer younger than age 50
Developing colorectal cancer, endometrial cancer, or other type of cancer* with mismatch repair deficiency (MMR-D) or microsatellite instability (MSI) found after testing of a sample of the tumor
Developing colorectal cancer and other types of cancer* linked with Lynch syndrome separately or at the same time
Colorectal cancer in 1 or more first-degree relatives who also has or has had another Lynch syndrome-related cancer*, with 1 of these cancers developing before age 50. The phrase “first-degree relatives” includes parents, siblings, and children.
Colorectal cancer in 2 or more first- or second-degree relatives with another Lynch syndrome-related cancer*. “Second-degree relatives” include aunts, uncles, grandparents, grandchildren, nephews, and nieces.
*category includes colorectal cancer, endometrial cancer, ovarian cancer, stomach cancer, small bowel cancer, ureter or renal pelvis cancer, bladder cancer, bile duct cancer, pancreatic cancer, or sebaceous adenomas of the skin
The definition of Lynch syndrome is still evolving. Many individuals may still have Lynch syndrome even if their family history does not fully match the revised Bethesda guidelines. Therefore, talking with a health professional who has training in genetic diseases and conditions is recommended for people who have a family history that suggests the possibility of Lynch syndrome.
Other forms of Lynch syndrome
Muir-Torre is another name for Lynch syndrome when people develop uncommon skin lesions or tumors, including sebaceous adenomas, sebaceous epitheliomas, sebaceous carcinomas, and keratocanthomas. Because these rare skin lesions are seen more commonly in people with Lynch syndrome, it is recommended that a person diagnosed with these lesions receive a genetic evaluation from a trained health professional.
Turcot syndrome is a condition in which people develop brain tumors and colorectal cancers. In some cases in the past, a person with Lynch syndrome and/or another genetic syndrome called familial adenomatous polyposis (FAP) have each been referred to as having Turcot syndrome. However, Turcot syndrome is no longer considered to be a distinct genetic syndrome.
What causes Lynch syndrome?
Lynch syndrome is a genetic condition. This means that the cancer risk can be passed from generation to generation in a family. These types of alterations, or mutations, to a gene are called "inherited mutations." Another name is germline mutations. Alterations in several genes involved in DNA mismatch repair that have been linked to Lynch syndrome. They include the genes of MLH1, MSH2, MSH6, PMS2, and EPCAM. A mutation in any of these genes gives a person an increased lifetime risk of developing colorectal cancer, endometrial cancer, ovarian cancer, and other related cancers.
Not all families that appear to have Lynch syndrome will have identifiable alterations in MLH1, MSH2, MSH6, PMS2, or EPCAM, and genetic testing for other forms of inherited cancer risk may be recommended for individuals with certain histories of cancer in themselves and/or family members.
Some people will develop changes in these genes that are not inherited but occur due to the body’s aging process and other causes that are not well understood. These types of mutations are called "acquired mutations." If a tumor is found to have alterations in these genes, the person’s inherited DNA (usually a blood or saliva test) will also be tested for that abnormal gene. If the blood and tumor both have the changed gene, the condition is inherited rather than acquired, meaning other family members could be affected.
How is Lynch syndrome inherited?
Normally, every cell has 2 copies of each gene: 1 inherited from the mother and 1 inherited from the father. Lynch syndrome follows an autosomal dominant inheritance pattern, in which a mutation needs to happen in only 1 copy of the gene for the person to have an increased risk of getting that disease. This means that a parent with a gene mutation may pass along a copy of their normal gene or a copy of the gene with the mutation. Therefore, a child who has a parent with a mutation has a 50% chance of inheriting that mutation. A sibling or parent of a person who has a mutation also has a 50% chance of having the same mutation. However, if the parents test negative for the mutation (meaning each person’s test results found no mutation), the risk to the siblings significantly decreases but their risk may still be higher than an average risk.
Options exist for people interested in having a child when a prospective parent carries a gene mutation that increases the risk for this hereditary cancer syndrome. Preimplantation genetic testing (PGT) is a medical procedure done in conjunction with in-vitro fertilization (IVF). It allows people who carry a specific known genetic mutation to reduce the likelihood that their children will inherit the mutation. A person's eggs are removed and fertilized in a laboratory. When the embryos reach a certain size, 1 cell is removed and is tested for the hereditary condition in question. People can then choose to transfer embryos that do not have the genetic mutation. PGT has been in use for over 2 decades and has been used for several hereditary cancer predisposition syndromes. However, this is a complex procedure with financial, physical, and emotional factors to consider before starting. For more information, talk with an assisted reproduction specialist at a fertility clinic.
How common is Lynch syndrome?
Most colorectal cancer is sporadic, meaning it occurs by chance with no known cause. Approximately 3% of all cases of colorectal cancer and 2% to 3% of all cases of endometrial cancer are thought to be due to Lynch syndrome.
How is Lynch syndrome diagnosed?
Lynch syndrome can be confirmed through a blood or saliva test of someone's inherited DNA. The test can determine if someone carries a mutation that can be passed down (called heritable) in 1 of the genes associated with Lynch syndrome. Currently, testing is available for the MLH1, MSH2, MSH6, PMS2 and EPCAM genes. However, not all families with Lynch syndrome will have an identifiable mutation in 1 of these genes.
Screening tests can also be performed on the cancerous tissue to determine if Lynch syndrome is likely. The 2 screening tests suggested are microsatellite instability testing (MSI) and immunohistochemistry testing (IHC). The results of these tests can indicate whether more specific genetic testing should be considered.
What are the estimated cancer risks associated with Lynch syndrome?
General lifetime cancer risks for people with Lynch syndrome
Colorectal cancer 20% to 80%
Stomach cancer 1% to 13%
Small bowel cancer (intestines) 1% to 6%
Pancreatic cancer 1% to 6%
Cancer risks for women with Lynch syndrome
There is a rapidly growing amount of data on how different individuals with Lynch syndrome have different risks of various cancers depending on the gene in which an individual carries a mutation. For example, studies have shown that individuals with Lynch syndrome with MSH2 mutations have higher risks of urinary tract cancer compared to individuals with other forms Lynch syndrome. Additionally, recent data suggest that people with Lynch syndrome with germline PMS2 mutations may have substantially lower risks of cancer than the estimates quoted above.
What are the cancer screening options for Lynch syndrome?
ASCO recommends the following screening for people with Lynch syndrome. It is important to discuss these options with your doctor, as each individual is different:
General screening and risk-reduction guidelines
Colonoscopy every 1 to 2 years, beginning between the ages of 20 to 25 or 5 years younger than the earliest age at diagnosis in the family, whichever is sooner
Upper endoscopy every 3 to 5 years, in addition to testing for Helicobacter pylori infection at a baseline exam with treatment if positive
Annual total body skin examination
Consideration of a daily aspirin, which has been linked to a significantly reduced risk of colorectal cancer in individuals with Lynch syndrome
Screening for other cancers linked with Lynch syndrome may be recommended depending on a person’s family history, though the effectiveness of such screening remains unproven.
Yearly female pelvic examination, pelvic ultrasound, endometrial biopsy, from age 30 to 35. After finished having children, the patient may want to consider having preventive surgery to remove the uterus and ovaries, especially since screening for endometrial and ovarian cancer has never proven to be effective in those with Lynch syndrome.
Screening options may change over time as new technologies are developed and more is learned about Lynch syndrome and its other forms. It is important to talk with your doctor about appropriate screening tests.
Learn more about what to expect with common tests and procedures.
Questions to ask the health care team
If you are concerned about your risk of colorectal cancer or other types of cancer, talk with your health care team. It can be helpful to bring someone along to your appointments to take notes. Consider asking your health care team the following questions:
What is my risk of developing colorectal cancer or other types of cancer?
What can I do to reduce my risk of cancer?
What are my options for cancer screening?
If you are concerned about your family history and think your family may have Lynch syndrome, consider asking the following questions:
Does my family history increase my risk of colorectal cancer or other types of cancer?
Does my family history increase my risk of skin cancer or other skin problems?
Have MSI or IHC tests been done on my tumor tissue?
Should I meet with a genetic counselor?
Should I consider genetic testing?
To find a genetic counselor in your area, ask your health care team or visit the following website: