In the clinic, many patients will have similar questions. Why? A colonoscopy reveals an occupancy in the colon, which is a growth in the large intestine, commonly a polyp, adenoma or cancer. Each type of mass is in turn different in size and appearance (tipped, subtipical or broad-based) and location (about 1.5 meters in the large intestine, divided into ascending, transverse, descending, sigmoid and rectum). All these factors are possible reasons for not directly resecting. Specifically: 1. The most common and important reason is that the examining physician finds a mass, but it is not good to determine the type, especially if it is larger than 1 cm, without a tip, with a bad appearance, or suspicious of cancer. It is necessary to take biopsy first to clarify the nature and see if it is cancerous, and then determine the surgical removal method. If the polyp is removed directly without considering whether it is malignant or not, then this treatment is very arbitrary and blind, and the result is non-standardized treatment, which is fine if it is a benign polyp, but in case it is cancerous and has residue, it needs to be operated again, and it will make the treatment difficult again. 2. Colonoscopic treatment is much more difficult and time-consuming than examination. It requires a specialized experienced and qualified endoscopist to do it. However, the operation of ordinary colonoscopy can be done by a trained endoscopist in general. Therefore, general physicians neither can nor should go for treatment even if they find problems. 3. Some endoscopic resection procedures have a higher risk of complications. For example, the tumor is large, or the lesion is extensive, or multiple masses are removed. This requires inpatient surgical treatment, and is not something that can be solved by outpatient endoscopy. Postoperative treatment such as fasting and hemostasis are required.