Small cell lung cancer is a common type of lung cancer with the following characteristics: Small cell lung cancer accounts for only a small percentage of primary lung cancer, roughly 15%. Smoking is the main predisposing factor for small cell lung cancer. The tumor cells of small cell lung cancer are smaller in size under the microscope and have large nuclei that fill almost the entire cell body. Although the cells are small, they are very aggressive and the cells will replicate and expand rapidly on their own. Therefore, the tumors are large when detected clinically and often invade large blood vessels and main bronchi, while mediastinal lymph nodes and distant metastases occur earlier. Small cell lung cancer may have enlarged hilar and mediastinal lymph nodes at a very young age, and there may be significant weight loss. Small cell lung cancer is also often combined with paraneoplastic syndromes, which are specific endocrine manifestations that are more likely to occur in small cell lung cancer than in non-small cell lung cancer because of the greater cellular activity of small cell lung cancer. The clinical evaluation of small cell lung cancer is the same as that of non-small cell lung cancer, including clinical presentation, imaging data, and tissue biopsy. After information is obtained, the clinical staging system for small cell lung cancer is different from that for non-small cell lung cancer: Small cell lung cancer is divided into only two stages: Limited disease: In this type of small cell lung cancer, tumor invasion is limited to one side of the lung, and even if there are lymph node metastases, they are limited to the side of the tumor. The extent of tumor invasion at this point can often be surrounded by a single radiation treatment field. Limited small cell lung cancer accounts for about 30% of all small cell lung cancers. Extensive non-small cell lung cancer: This stage of small cell lung cancer has breached the affected thoracic cavity, such as pericardial effusion, pleural effusion, or distant metastases. Roughly 70% of small cell lung cancers are already extensive by the time they are diagnosed. This two-stage approach is very helpful and concise for the treatment of small cell lung cancer. Of course, there is now a TNM staging system for small cell lung cancer, but it appears to be too complex and has little significance in guiding treatment. Because the prognosis of small cell lung cancer is extremely poor, the vast majority of diagnosed cases are referred to the non-surgical treatment sequence, and the internal medicine treatment options do not differ much for different TNM stages of small cell lung cancer, so excessive staging is meaningless.