Lung cancer staging is a method to define the extent of cancer dissemination. Staging is very important and is the basis for deciding and treatment means and judging the prognosis of lung cancer. Commonly used tools for staging lung cancer patients include chest CT, head MRI, ultrasound of abdomen and double supraclavicular lymph nodes, bone scan and a series of other tests. If necessary, some invasive methods such as TBNA and mediastinoscopy are also used. Staging of non-small cell lung cancer: The most commonly used system to describe the growth and spread of non-small cell lung cancer is the TNM staging system. In TNM staging, information about the tumor, nearby lymph nodes and distant organ metastases is combined, and staging is used to refer to a specific TNM grouping. Subgroup staging is described using the number 0 and the Roman numerals I through IV. T stands for tumor (its size and degree of spread within the lung and adjacent organs), N stands for lymph node spread, and M stands for metastasis (spread to distant organs). T-staging of non-small cell lung cancer: T grading is based on the size of the lung cancer, its spread and location within the lung, and the extent of spread to adjacent tissues. N-staging of non-small cell lung cancer: N-staging depends on which nearby lymph nodes the cancer has invaded. Staging of small cell lung cancer: Although small cell lung cancer can be staged like non-small cell lung cancer, the vast majority of physician practitioners find the simpler stage 2 system to be better in terms of treatment options. This system divides small cell lung cancer into “limited” and “extensive” stages. Limited stage means that the cancer is confined to one lung and the lymph nodes are located on the same side of the chest, while extensive stage occurs if the cancer has spread to the other lung, or to lymph nodes in the opposite side of the chest, or to distant organs, or if there is malignant pleural fluid.