Symptoms of early-stage gastric cancer are generally not very obvious. Some patients may experience subtle symptoms resembling those of gastritis or gastrointestinal ulcers, including non-specific gastrointestinal symptoms such as discomfort and bloating in the upper abdomen, acid reflux, nausea, vomiting, and decreased appetite. In terms of pain, early-stage gastric cancer patients might only experience a sensation of bloating or mild tenderness in the upper abdomen. Severe pain is usually associated with late-stage gastric cancer, occurring when there is extensive abdominal metastasis or tumor progression, and the tumor is large enough to cause significant pain, requiring analgesics for treatment.