Lynch Syndrome

What is Lynch syndrome?

Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), is a type of inherited cancer of the digestive tract. People who have Lynch syndrome have a significantly increased risk of developing colorectal cancer and an increased risk of developing other types of cancers, such as endometrial (uterine), stomach, breast, ovarian, small bowel (intestinal), pancreatic, prostate, urinary tract, liver, kidney and bile duct cancers.

Lynch syndrome is a possible diagnosis when multiple people on the same side of the family diagnosed with colorectal cancer. In addition, cancer is more likely to be diagnosed at a young age. The average age for colorectal cancer to be diagnosed in someone with Lynch syndrome is 45, as compared with the average age of 72 for a new diagnosis of colorectal cancer in the general population. In Lynch syndrome, colorectal cancer is somewhat more likely to develop on the right side of the colon.

ASCO recommends tumor testing for Lynch syndrome in all patients with colorectal cancer. As an alternate option, tumor testing is recommended for people who develop colorectal cancer younger than 70, or for those who are older than 70 and meet any of the revised Bethesda guidelines (see below). There is also an increased risk of a person with Lynch syndrome to develop multiple cancers during his or her lifetime. Read more about these recommendations and the recommendations for screening listed below at www.asco.org/endorsements/HereditaryCRC.

What are the signs of Lynch syndrome?

One set of criteria used to identify Lynch syndrome are called the revised Bethesda guidelines, which are listed below:

• Developing colorectal cancer younger than age 50
• Developing colorectal cancer and other cancers* linked with Lynch syndrome separately or at the same time
• Developing colorectal cancer with tumor features linked to Lynch syndrome at an age younger than 60
• Colorectal cancer in one or more first-degree relatives who also has or has had another Lynch syndrome-related cancer^*, with one of these cancers developing before age 50
• Colorectal cancer in two or more first- or second-degree relatives with another Lynch syndrome-related cancer.^*(colorectal cancer, endometrial cancer, small bowel, ureter, or renal pelvis cancer; some people would also consider including ovarian cancer)

The definition of Lynch syndrome is still evolving. A family may still have Lynch syndrome even if the revised Bethesda guidelines do not fully match the family history. Therefore, meeting with a health professional who has training in genetic diseases and conditions, such as a genetic counselor or medical geneticist, is recommended for people who have a family history that suggests Lynch syndrome.

There are two variant forms of Lynch syndrome called Muir-Torre syndrome and Turcot 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. Several genes have been identified that are linked to Lynch syndrome. They include MLH1, MSH2, MSH6, PMS2, and EPCAM. A mutation (alteration) in any of these genes gives a person an increased lifetime risk of developing colorectal cancer and other related cancers. Women also have an increased risk of developing endometrial and ovarian cancers (Cancer.Net).