Descriptive epidemiology of hereditary non-polyposis colorectal cancer

Hereditary non-polyposis colorectal cancer (HNPCC or Lynch syndrome) is characterized by early occurrence of colorectal malignancies, localization of tumors in the proximal colon, frequency of multiple primaries (both synchronous and metachronous) and an autosomal dominant type of genetic transmission. HNPCC has been reported in many races and populations, including Japanese, Philipinos and American Indians. The frequency off the disease ranges between 1 and 5% of all colorectal malignancies. In northern Italy, the frequency of HNPCC has been estimated in the order of 2.8-3.0% of all registered cancers of the large bowel, while lower estimates have been recorded in southern regions. The identification of HNPCC remains difficult, mainly because the full-blown syndrome does not become manifest until several family members are affected with cancer. The recent identification of at least four genes responsible, when mutated, for the clinical spectrum of Lynch syndrome should be of considerable help in recognizing this type of tumors in the general population.