More than 95% of colorectal cancer pathologies are adenocarcinomas. Approximately 90% of colorectal cancers originate from adenoma cells. Adenomas appear as polypoid bulging lesions to the naked eye or endoscopically. Malignant transformation of colorectal adenomas to cancer often takes 5 to 10 years, involving multiple genetic mutations and multiple steps of evolution (Figure). Therefore, colorectal cancer can be effectively prevented if intestinal polyps are detected early and removed before they become malignant by performing colonoscopy screening. To date, the gold standard for confirming the diagnosis of any kind of tumor is still pathological diagnosis. In other words, morphological characteristics of tumor tissues and tumor cells need to be observed under microscope and combined with immunohistochemical staining if necessary to clarify the diagnosis. Surgery, radiotherapy, chemotherapy and targeted drugs for tumor treatment need to be carried out only after pathological diagnosis is obtained, otherwise misdiagnosis and mistreatment or over-treatment may occur. The diagnosis of tumor derived from CT, MRI or endoscopic visual observation alone is not completely reliable. This is why some patients with tumors on colorectum repeatedly undergo colonoscopy to take biopsies. If the biopsy specimens do not reveal cancer cells or cancer tissue types under microscope, then the subsequent treatment cannot be carried out correctly.