Identification of an HNPCC family.

Hereditary nonpolyposis colorectal cancer (HNPCC) families are frequently missed in the clinical practice setting. The events leading to the diagnosis of a new HNPCC family are described, with particular attention to the importance of a detailed and extended pedigree, and the delivery of pertinent educational and cancer control recommendations to family members. Clinical clues suggestive of HNPCC include young age at colon cancer onset (< 45 yr), proximal colon cancers, multiple colon cancer, and a family history of colonic cancer or certain extracolonic cancers, including endometrium, stomach, small bowel, and urinary tract. Once the diagnosis is established, management of high-risk patients must be based on an awareness of these cardinal features. The recent identification of the cancer susceptibility locus at chromosome 2p15-16 for a subset of HNPCC families and its cloning should lead to a blood test for the carrier state. HNPCC families must nevertheless be identified before high risk family members can enjoy the benefits of progress in molecular biology. This HNPCC family report illustrates some of the important clues necessary for recognizing such families, and the logistics of detailed evaluation.