EDITOR—Hereditary non-polyposis colorectal cancer (HNPCC) is a heterogeneous autosomal dominant disease with incomplete penetrance. The frequency is estimated at 1:200/1:1000. HNPCC results from constitutional mutation in one of the five human mismatch repair genes (MMR) that have so far been implicated: hMSH2, hMLH1, hPMS1, hPMS2, and hMSH6. 2 hMSH2 and hMLH1 account for the majority of mutati...
