Colorectal cancer is the most prevalent cancer and the third cancer related death in Taiwan. Adenoma is a precancerous lesion of colorectal cancer. Using colonoscopy to detect and remove the adenoma has a chance to prevent colorectal cancer development.

In the resection of colorectal polyps, for medium and large polyps that are more than one centimeter and less than two centimeters, because these polyps are at risk of cancer, they currently use hot-snaring polypectomy or more advanced endoscopic mucosal resection. Resection of such tumors ensures that a sufficient depth of resection and a high complete resection rate (R0 resection) are achieved.

Flat serrated adenoma (sessile serrated lesion) is a special adenoma that accounts for 10-12% of all colorectal polyps. Different from traditional adenomas, flat serrated adenomas within two centimeters in size have very little chance of becoming cancerous. And we know that on removal of medium and large polyps of 10-20mm, compared with the cold snaring polypectomy, the postoperative bleeding of the hot-snaring polypectomy technique is higher. Therefore, when removing low-risk polyps such as flat serrated adenomas, we may choose using a non-energized technique with low complications and we then would like to know whether the complete resection rate can be achieved by using the non-energized technique in the resection of a flat serrated adenoma of 10-20 mm, despite the large size, and compare the success rate and complications with traditional hot snaring polypectomy.

This study is a single-country, multi-center, randomized controlled study. The subjects of the case were patients who underwent colonoscopy for various indications and found flat serrated adenomas ranging in size from 10-20 mm during the procedure. Excluded criterias are patients who are younger than 20 years old and have contraindications for colonoscopy. All patients included in the study will sign the informed consent sheet at the outpatient clinic. Once a flat serrated adenoma with a size of 10-20 mm is found during colonoscopy, the subjects will be randomly assigned to Cold snaring polypectomy group, cold endoscopic mucosal resection group or hot endoscopic mucosal resection group.

The preoperative preparation for bowel cleansing and colonoscope insertion method for these three groups of patients are totally the same as those of general colonoscopy. The only difference is the resection method flat serrated glands of 10-20 mm. The tumor was resected by cold snaring polypectomy, one group was resected by cold endoscopic mucosal resection, and the other group was resected by hot endoscopic mucosal resection. The endoscopists participating in this research project have extensive experience in endoscopy and perform at least one hundred polypectomy operations every year. The excised tumor will be sent to the pathology department for pathological diagnosis, and the pathology doctor will judge the completeness of the tumor resection

Inclusion Criteria:

1. Age older than 20 years old
2. Indicated for colonoscopy and willing to receive colonoscopy examination and polyp resection。
3. Any Sessile serrated adenoma size between 10-20mm was found during the examination。

Exclusion Criteria:

1. Age younger than 20 years old
2. Contraindication for colonoscopy or polypectomy (Such as recent acute myocardial infarction, pulmonary embolism ,coagulopathy..)