Colorectal cancer is the most common gastrointestinal cancer worldwide.In recent20years, the incidence of colorectal cancer is increasing in most contries of the world. In our country colerectal cancer has the same status,the incidence rate of which ranks third place among all kinds of malignant neoplasm. Metastasis is the most important cause of death for malignant tumors, including colorectal cancer.Ninety percent deaths of cancer are due to metastatic disease. Lymph node metastasis is the main metastasis...