Hereditary nonopolyposis colorectal cancer (HNPCC) or Lynch Syndrome is caused by a mutation in the genes that are responsible for DNA repair. People that have this condition have up to an 80% chance of developing colorectal cancer during their lifetime. There is also an increased risk for developing other types of cancer such as endometrial, stomach, urinary tract, ovarian, small bowel, biliary tract, brain, and sebaceous adenomas. Women may develop endometrial cancer before colorectal cancer.
The first step in diagnosis is collecting a family history that includes three generations if possible. HNPCC is suspected when colorectal cancer occurs in an indivual under 50 years of age, or there is colorectal, or related cancers, such as stomach, urinary or female reproductive system in several closely related family members. A blood test can determine if the alterted genes are present.
For individuals that are diagnosed with HNPCC regular screening, with colonscopies starting between 20-25 years of age are important. Other screening recommendations may include upper endoscopies, pelvic ultrasound, and enodmetrial biopsies.
Familial adenomatous polyposis (FAP) is an inherited colorectal cancer syndrome that causes the colon to be blanketed with hundreds to thousands of polyps usually starting in the teenage years. Another type of FAP, Attenuated FAP, is characterized by fewer polyps and a later age of onset. Individuals with this condition have almost a 100% chance of developing colorectal cancer if they are not properly diagnosed and treated. Other manifestations of FAP include polyps in the small bowel and stomach, skin tumors, extra teeth, benign bony tumors usually seen in the skull or jaw, and rarely brain tumors.
Individuals with FAP or aFAP require close medical supersvision and treatment which usually involves removal of all or part of the colon and rectum. Any remaining colon or rectal tissue must be examined on a yearly basis. Other screening recommendations may include endoscopy of the stomach and duodenum, and thyroid and skin examinations.