Black stools are not necessarily a pre-cancer condition, as black stools can also occur in some other diseases, such as intestinal polyps and gastric ulcers. Black stools can be seen in a variety of conditions that cause bleeding in the digestive tract, not just cancer. When gastrointestinal bleeding occurs and the blood stays in the intestines for a longer period of time, it may cause black stools, such as gastric ulcers, cirrhosis bleeding, intestinal polyps, enteritis and other diseases. In addition to disease factors, black stools may also occur after consuming blood products, or taking medications such as iron or bismuth for stomach problems. However, black stool can also occur in cancer, such as gastric cancer patients, when the tumor invades the surrounding blood vessels, or the tumor itself has necrosis and bleeding, black stool will occur, at this time, the patient may be accompanied by symptoms such as malignant disease, abdominal pain and so on, and usually the doctor can distinguish them by taking pictures, taking pathology and other examinations. Therefore, it is recommended to go to the gastroenterology department in time when black stools appear, it is not necessarily cancer, and even in the unlikely event that it is diagnosed as cancer, it is better to treat it as early as possible.