Patients with stomach cancer usually experience abdominal pain during the course of the disease. Most of the early stage stomach cancer patients have no symptoms and it is hard for patients to notice. As the disease progresses, patients will experience some symptoms similar to indigestion, such as upper abdominal discomfort, fullness and indigestion. Some patients may experience vague pain in the upper abdomen, and with the aggravation of the disease, this pain may be progressively aggravated. Patients may feel continuous vague pain or burning sensation in the upper abdomen, and some patients may experience unbearable and severe pain. Some patients may also experience sudden and severe abdominal pain, suggesting that it may be a manifestation of gastric perforation, when the abdominal contents enter the abdominal cavity, leading to chemical peritonitis and causing severe abdominal pain.