Hereditary Nonpolyposis Colorectal Cancer

Hereditary Nonpolyposis Colorectal Cancer (HNPCC, also known as Lynch syndrome) is the most common of the hereditary colon syndromes and runs in families which are affected. 



HNPCC occurs when there are mutations of MLH1 and MLH2, which are mismatch repair genes.  This type of colon cancer may occur at unusually young age and tends to occur in the right side of the colon.  Many families with HPNCC have high risk of other cancers, especially endometrial carcinoma and ovarian cancer.

To detect this type of colon cancer at early age, annual colonoscopy is recommended to begin at age 20 to 25, or 10 years prior to the earliest age of colon cancer diagnosed in the family.  Annual screening for endometrial cancer and ovarian cancer is also recommended.