Genetic counseling in hereditary nonpolyposis colorectal cancer.

Menko and colleagues review the genetic counseling that occurs after the presymptomatic diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC) is made. The discovery of the mechanism by which tumors develop in this setting and the cloning of the genes responsible for the disease have made possible the DNA-based diagnosis of a disease, which, less than 5 years ago, was a controversial entity. In a remarkably short period, the nature of HNPCC has been greatly elucidated, its relationship to defective DNA mismatch repair has become manifest, and the means to diagnose it in a presymptomatic state has been developed [1].