Molecular epidemiology of hereditary nonpolyposis colorectal cancer in Finland

The population frequency of germline mutations predisposing to hereditary nonpolyposis colorectal cancer (HNPCC) is unknown. Several epidemiological studies have addressed the problem, and estimates on the proportion of the total colorectal cancer burden accounted for by HNPCC have varied between 0.5% and 13%. In the absence of any clinical diagnostic hallmarks, the definition of HNPCC is based on family history. The problem in defining the syndrome is reflected in the wide range of frequency estimates. The molecular background of HNPCC has recently been clarified. Defects in a total of five different mismatch repair genes have been associated with the syndrome. Tumors associated with HNPCC display microsatellite instability (or replication error, RER). RER analysis followed by germline mutation analysis in the mismatch repair genes allows molecular diagnosis in a proportion of HNPCC patients. These diagnostic methods are likely to contribute to our understanding of the epidemiology of HNPCC. In Finland, the centralized health care system, population history, and recent advances in molecular genetic research have together created tools to evaluate the molecular epidemiology of HNPCC in the country.