Why does lung cancer cause pain? There are two main reasons, one is the pain caused by the disease itself, and the other is the pain caused by treatment. The pain caused by lung cancer itself is mainly caused by compression, invasion and metastasis. Tumor compression to organs, or compression to surrounding nerves, blood vessels and lymphatic vessels can cause pain. And tumor invasion of nerves, blood vessels and pleura can also cause pain. Lung cancer easily metastasizes to pleura and causes chest pain. The pain symptoms caused by lung cancer metastasis to other parts, especially the bones of the whole body, are especially obvious. In addition, certain metabolites of tumor cells, such as the increase of hydrogen ions, rupture and bleeding of the tumor itself, perforation, infection and other factors can cause pain. Treatment-induced pain, on the other hand, is the pain caused by surgery, radiotherapy, chemotherapy, etc. Pain in the wound after surgery may last for days and months. Pain after swallowing caused by radiation esophagitis due to radiotherapy, etc. Some chemotherapy drugs can cause peripheral neuralgia, leaving patients with numbness in the extremities, abdominal pain and burning pain in the hands and feet. In small pulmonary nodules, these factors are almost absent, and all will not be felt as significant pain.