A submucosal mass 10cm from the anus seen by colonoscopy is serious if it is a tumor; less serious if it is a polyp, etc. If a submucosal mass 10cm from the anus is biopsied and found to be a tumor, it is diagnosed as rectal cancer. Rectal cancer is a malignant tumor of the rectum, which is a serious disease, and the earlier it is detected and treated, the better the result will be. At present, the most important treatment for rectal cancer is still surgery. A mass 10cm away from the anus can be treated with low anterior resection, which is a kind of anus-preserving surgery for rectal cancer. If the biopsy of the mass shows that it is not a tumor but another type of lesion, such as a polyp, it is less serious. However, certain types of polyps, such as adenomas, can become cancerous in about half of cases, so early endoscopic removal is recommended. If a rectal submucosal mass is detected 10cm from the anus by colonoscopy, it is recommended to make a clear diagnosis as soon as possible, give reasonable treatment, and follow the doctor’s instructions to avoid delaying the aggravation of the condition.