Hereditary nonpolyposis colorectal cancer

Lynch syndrome (HNPCC or hereditary nonpolyposis colorectal cancer ) is an autosomal dominant genetic condition that has a high risk of colon cancer as well as other cancers including endometrial cancer (second most common), ovary, stomach, small intestine, hepatobiliary tract, upper urinary tract, brain, and skin. The increased risk for these cancers is due to inherited mutations that impair DNA mismatch repair. It is a type of cancer syndrome.

Terminology

Henry T. Lynch, Professor of Medicine at Creighton University Medical Center, characterized the syndrome in 1966. In his earlier work, he described the disease entity as "cancer family syndrome." The term "Lynch syndrome" was coined in 1984 by other authors; Lynch named the condition HNPCC in 1985. Since then the two terms have been used interchangeably, until later advances in the understanding of the genetics of the disease led to the term HNPCC falling out of favour.

Other sources reserve the term "Lynch syndrome" when there is a known DNA mismatch repair defect, and use the term "familial colorectal cancer type X" when the Amsterdam criteria are met but there is no known DNA mismatch repair defect. The putative "type X" families appear to have a lower overall incidence of cancer and lower risk for non-colorectal cancers than families with documented DNA mismatch repair deficiency. About 35% of patients meeting Amsterdam criteria do not have a DNA-mismatch-repair gene mutation.

Colorectal cancer

Colorectal cancer (also known as colon cancer, rectal cancer, or bowel cancer) is the development of cancer in the colon or rectum (parts of the large intestine). It is due to the abnormal growth of cells that have the ability to invade or spread to other parts of the body. Signs and symptoms may include blood in the stool, a change in bowel movements, weight loss, and feeling tired all the time.

Risk factors for colorectal cancer include lifestyle, older age, and inherited genetic disorders. Other risk factors include diet, smoking, alcohol, lack of physical activity, family history of colon cancer and colon polyps, presence of colon polyps, race, exposure to radiation, and even other diseases such as diabetes and obesity. Genetic disorders only occur in a small fraction of the population. A diet high in red, processed meat, while low in fiber increases the risk of colorectal cancer. Other diseases such as inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis, can increase the risk of colorectal cancer. Some of the inherited genetic disorders that can cause colorectal cancer include familial adenomatous polyposis and hereditary non-polyposis colon cancer; however, these represent less than 5% of cases. It typically starts as a benign tumor, often in the form of a polyp, which over time becomes cancerous.