Early stage of lung cancer is often asymptomatic, but how to detect early stage of lung cancer is mainly to do lung CT scan to find out whether there are ground glass nodules or soft tissue masses in the lung. The so-called early stage lung cancer is defined as tumor ≤ 3cm, no hilar lymph node metastasis, no mediastinal lymph node metastasis, and no distant metastasis. Lung tumors of this size are often asymptomatic and are mainly detected by regular lung CT examinations. Especially if you have a long history of smoking or a family history of lung cancer, regular lung CT screening is beneficial to detect early lung cancer. For ground glass nodules or soft tissue masses found by lung CT, puncture biopsy or fiberoptic bronchoscopy should be done as soon as possible to clarify whether it is lung cancer, which can serve the purpose of early detection, early diagnosis and early treatment.