Identifying Hereditary Nonpolyposis Colorectal Cancer

The recent discovery of the genetic basis of certain familial aggregations of colorectal cancer validated 90 years of clinical observation suggesting that such aggregations are hereditary.1 It also promised the ability to detect asymptomatic carriers of the deleterious genes, with attendant gains in the control of cancer. Our ability to act on that promise has been held back by the need for answers to two difficult questions: How common are the mutations of interest, and who should be tested for them? The work of Aaltonen et al.,2 reported in this issue of the Journal, provides some valuable answers.Germ-line mutations . . .