Hereditary nonpolyposis colon cancer (HNPCC), also known as Lynch syndrome, is a type of inherited cancer of the large intestine. People who have HNPCC are at increased risk for developing small growths of excess tissue (polyps) in the large intestine early in life, making it more likely the growths will become cancerous.

A person with HNPCC may develop colon cancer at an early age (before age 50).

HNPCC is strongly suspected when:

• Three or more family members have colorectal cancer (one of whom is a first-degree relative).
• One or more family members has had colorectal cancer before the age of 50.
• Colorectal cancer involves two or more generations.

A genetic test can tell if a person carries the gene for HNPCC.