大肠癌在我国乃至全世界是一常见的恶性肿瘤 ,近年随着人们生活条件及饮食结构的改变 ,其发病有明显上升的趋势。我国每年新增病例约 2 5万 ,占恶性肿瘤发病率的第 4位 ,发达地区已上升到第 3位。遗传性非息肉病性大肠癌 (HNPCC)是一种特殊类型的大肠癌 ,它是由于DNA错配修复基 Colorectal cancer is a common malignant tumor in our country and even in the world. In recent years, with the change of people’s living conditions and diet structure, the incidence of colorectal cancer has obviously increased. In our country, there are about 25,000 new cases each year, accounting for the fourth in the incidence of malignant tumors and the third in developed areas. Hereditary nonpolyposis colorectal cancer (HNPCC) is a special type of colorectal cancer, it is due to DNA mismatch repair base