Lung cancer is difficult to detect early because the symptoms are not obvious, however, if people have sufficient health awareness, lung cancer can still be traced. 1. If cough only lasts for one to two weeks, it may be caused by cold or inflammation. However, if it lasts more than two weeks, coughing sputum or blood in sputum, it is better to go to hospital to rule out the possibility of tumor. Those with family history, or smokers, should pay more attention to this symptom. 2.Because the lung is closer to the neck and shoulder, its pain is sometimes mistaken for frozen shoulder or cervical spondylosis. Some people even had physiotherapy for more than half a year and turned to check the lung because the effect was not obvious, only to find out it was lung cancer. 3.Lung cancer may sometimes manifest as unexplained bone and joint pain, which is called “extra-pulmonary manifestation” in medical terminology, not bone metastasis of cancer cells as people think. However, “extra-pulmonary manifestation” is relatively rare. 4.People over 40 years old should have CT examination once a year to keep a good medical check.