Lung cancer metastasized to the brain is stage IV. There are two staging methods for lung cancer, which are: clinical staging and TNM staging; among them, clinical staging is divided according to TNM staging, i.e., after clarifying TNM staging, it is then categorized into clinical staging. The specific staging is as follows: 1. Clinical staging, often divided into: occult cancer, stage 0, stage I (A, B), stage II (A, B), stage III (A, B, C), stage IV (A, B). 2. TNM staging: T is Tumor, which is used to distinguish the size of the primary tumor; N is Node, which is used to distinguish the metastasis of regional lymph nodes, the location and extent of the metastasis; M is Metastasis, which is used to distinguish the metastasis of tissues and organs other than the primary tumor. All of the above are combined with numbers and letters to indicate different degrees, such as T1N0M0 and so on. Lung cancer patients found with distant metastasis, regardless of whether the site of metastasis is in the chest cavity or not, i.e. M1, and regardless of the size of tumor (T) and whether there is lymph node metastasis or not (N), all of them are uniformly categorized into clinical stage IV, i.e. advanced stage. Warm reminder: patients who have found tumors should listen carefully to the diagnosis and treatment suggestions of specialists and establish confidence in treatment.