IDENTIFYING PATIENTS AT RISK FOR HEREDITARY NONPOLYPOSIS COLON CANCER (HNPCC)
Once accurate family history information has been obtained and you identify individuals at risk for HNPCC, genetic testing may be appropriate. The American Society of Clinical Oncology (ASCO) issued guidelines for cancer susceptibility testing, which stated that testing should only be offered when:

	The individual has personal or family history feature suggestive of a genetic cancer susceptibility condition
	The test can be adequately interpreted
	The results will influence the medical management of the patient or family

The following features indicate a high likelihood that a patient carries an HNPCC mutation and warrants consideration for genetic susceptibility testing:

Personal or family history of -

	Colorectal cancer diagnosed before age 50
	Endometrial cancer diagnosed before age 50
	2 or more HNPCC-related cancers in an individual or family
	Relatives of an HNPCC mutation carrier

Various criteria have been proposed to assist in the clinical diagnosis of HNPCC. These include the Amsterdam criteria and the Bethesda guidelines. However, these criteria have been shown to have limitations and are too stringent for clinical use. For example, the Amsterdam criteria were designed to identify families with the highest probability of having HNPCC. As a result, they have been shown to miss a significant amount of patients with HNPCC mutations. Thus, many clinicians use mutation prevalence data to assist in risk assessment for HNPCC. You can determine the chance of an MLH1 or MSH2 mutation based upon your patient's personal and family history by using the HNPCC Mutation Prevalence Tables. Prevalence data for MSH6 mutations are not yet available.

Click here to open the HNPCC Mutation Prevalence Table in PDF format.

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