Lynch syndrome

What causes Lynch syndrome?

Lynch syndrome is a hereditary condition caused by a genetic mutation that can be passed from a carrier to their child with a 50% probability. Lynch syndrome particularly increases the risk of colorectal cancer, but it is also associated with a higher risk of endometrial, stomach, urinary tract, ovarian, small bowel, breast, and biliary tract cancers.

Depending on the specific gene involved, carriers have, by the age of 75:

• A 15–46% risk of developing colorectal cancer

• A 43–57% risk of developing endometrial cancer

• A 10–17% risk of developing ovarian cancer

The history of Lynch syndrome

Lynch syndrome was first recognized over a century ago, in 1913. It was initially known as Cancer Family Syndrome. In the 1980s, an international research group studying the condition renamed it Hereditary Non-Polyposis Colorectal Cancer (HNPCC) syndrome. On the syndrome’s 100th anniversary in 2013, it was renamed Lynch syndrome in honor of the pioneering researcher Dr. Henry Lynch. Henry Lynch passed away at the age of 91 in June 2019.

Approximately 10,000 carriers in Finland

In the past, Lynch syndrome was identified based on the occurrence of characteristic cancers within families over several generations. On this basis, it was estimated that approximately 3% of all colorectal cancers are caused by Lynch syndrome-related gene mutations. Today, advances in genetic testing and biobank research allow for more accurate estimates of the prevalence of Lynch syndrome. The associated gene mutations are estimated to occur in as many as 1 in 340 people. This means that there are approximately 10,000 mutation carriers in Finland and an estimated one million across Europe.

A genetic mutation does not cause disease – it increases cancer risk

Many hereditary diseases are known to be associated with specific genetic mutations, but most of these conditions are rare. Compared with them, Lynch syndrome is relatively common. Heredity also plays an important role in many common diseases, but the development of disease is usually influenced by multiple factors. In this sense, Lynch syndrome lies somewhere between rare inherited disorders and common multifactorial diseases. The mutation itself does not cause any known chronic illness. Instead, it increases susceptibility to cellular changes that occur during cell division and may lead to cancer.

Regular surveillance reduces cancer risk

The increased cancer risk associated with Lynch syndrome appears to be greatest in organs where cells renew rapidly, such as the bowel, endometrium, and urinary tract. In some cases, cancers have also been identified in organs where cell division is less active. The prognosis of colorectal cancer in people with Lynch syndrome can be significantly improved through regular colonoscopy surveillance. Endometrial cancer can be almost entirely prevented through preventive surgery. For this reason, carriers should be identified as early as possible. Recognizing Lynch syndrome is important even if it is discovered only after the first cancer diagnosis, as this information can influence surgical decisions and cancer treatment planning.

Cancer is not inherited

It is important for carriers to understand their increased cancer risk and to commit to recommended surveillance. Information about the hereditary nature of the mutation should also be shared within the family. Cancer itself is not inherited. What is inherited is the genetic mutation that increases the risk of developing cancer. Lifestyle choices can also influence an individual’s overall cancer risk.

Lynchin syndrooma -opas