Lung cancer patients may have the clinical manifestation of stomach pain, and the following three reasons are considered: 1. Abdominal pain is caused by metastasis of lung cancer lesions, for example, the lesions have metastasized to the liver, which causes pressure pain in the liver area of the abdomen and loss of appetite. The lesion has metastasized to the peritoneum, causing cancer peritonitis, which is also clinically manifested as abdominal pain and fever. The lesions have been transferred to the abdominal organs, causing cancerous intestinal obstruction, which is mainly manifested as abdominal pain and abdominal distension.2. For the abdominal pain caused by the treatment of lung cancer, for example, after the use of chemotherapeutic drugs, due to the direct stimulation of chemotherapeutic drugs on the mucous membrane of gastrointestinal tract, the gastrointestinal mucous membrane undergoes spasms, which may cause abdominal pain. After the application of targeted drugs, patients will also have the side effects of abdominal pain, diarrhea and skin rash.3. Due to acute gastric mucous membrane lesion caused by lung cancer, patients will not only vomit blood and have black stool, but also have the clinical symptom of stomach pain.