Patients with lung nodules may develop a variety of potentially severe symptoms. These symptoms may impact a patient's quality of life and lead to difficult treatment. Through this research program, the investigators want to understand the pathogenesis of the changes of these symptoms.

Lung nodules can manifest as single or multiple independent lung consolidation shadow in form of quasi-circular. These lung nodules are surrounded by normal lung tissues, and will not cause pulmonary atelectasis. In some early standards, all the quasi-circular shadows within 6cm found in lung are categorized as lung nodules. However, according to current standards, the lesion within 3cm can be identified as lung nodules. With widespread use of lung cancer CT screening, lung nodules were identified more and more frequently.

What is the optimal way to manage this CT finding? Should we adopt surgical removal or just observation? An optimal solution is to determine a clearly defined standard of care that is easy to learn. We propose a method called "three plus two". The 'Three' is a three-step testing method, and the 'Two' means two alternative solutions. Three-step testing method includes collecting medical history, non-invasive examination, and invasive examination. The two alternative solutions are surgical removal and follow-up observation. We have independently developed an application based on a smartphone platform. This platform will provide a novel evidence-based research method for observing the dynamic evolution of the lung nodules in patients. There have been no prior studies about managing this CT scan finding, either in China or internationally.

Inclusion Criteria:

• Age between 18 and 90
• There is a chest lesion less than 3cm width (examined by Thin-Section CT)
• The patient or his family member owns a smartphone
• Signed informed consent
• Completed the installation and registration of mobile terminal software online
• Willing to complete a 10-year period of follow-up

Exclusion Criteria:

• Not equipped with a smartphone
• Cannot complete the installation or registration of smartphone application software online
• Received prior chemotherapy medications for lung cancer or received lung surgical removal treatment

Approximately 10,000 patients will participate in this research program, in 100 different medical institutions.