Vomiting blood is not necessarily cancer. By vomiting blood, we mean vomiting bloody material from inside the stomach. Blood is digested by gastric juice and turns into coffee grounds-like black material, so vomiting blood is usually coffee grounds-like black or dark brown material. If the bleeding is heavy and rapid, the vomited blood may also be dark red or even with blood clots. There are many causes of vomiting blood, the most common being bleeding peptic ulcers, including gastric ulcers and duodenal ulcers, which cause hemorrhage when the ulcer invades a larger blood vessel and manifests itself as vomiting blood. In some patients with cirrhosis, obstruction of portal venous return leads to varices in the esophageal plexus at the fundus of the stomach, which suddenly rupture can also lead to hematemesis. Others, such as damage to the gastric mucosa caused by heavy alcohol consumption, can lead to vomiting of blood. Of course, malignant tumors, especially gastric cancer and cirrhosis after hepatocellular carcinoma, can also lead to great vomiting of blood due to rupture of cancerous tissues. Therefore, vomiting blood is not necessarily cancer, but depends on the accompanying related symptoms for further diagnosis.