Many patients with lung tumors are diagnosed with lung cancer after chest X-ray, CT, MRI or other examinations, and doctors ask patients to take biopsy, lung aspiration biopsy, etc. before treatment. However, many patients think it is unnecessary and troublesome to take biopsy since they already have lung cancer and do not cooperate. Why do patients need to take biopsy after being diagnosed with lung cancer? This is because CT, MRI and X-ray are imaging diagnostics, the accuracy rate of which cannot reach 100%, let alone judging the nature of tumor. Besides, the classification of tumor is complicated, cytological examination is a secondary diagnosis, and it is difficult to make specific typing of tumor, while taking biopsy can make correct judgment on pathology. Clinically, common lung cancer pathology can be classified into four categories: small cell undifferentiated carcinoma, large cell undifferentiated carcinoma, squamous carcinoma and adenocarcinoma, the latter three are also called “non-small cell lung cancer” (NSCLC). The biological characteristics of each type of lung cancer are different, and the treatment options are not identical. Small cell lung cancer is more sensitive to chemotherapy and radiotherapy, but is prone to blood type metastasis; while squamous lung cancer is mainly lymph node metastasis and has a relatively good effect on radiotherapy; adenocarcinoma is less sensitive to radiotherapy and chemotherapy, so surgery should be performed if possible, and chemotherapy should be selected accordingly after surgery. The use of chemotherapy is different for different types of lung cancer. There is a big difference between chemotherapy regimens for small cell lung cancer and non-small cell lung cancer. Therefore, only with pathological diagnosis can we choose the correct treatment plan, so as not to take a “wrong turn” and achieve better treatment results. Biopsy can not only help in the treatment plan, but also provide a reference to judge the prognosis of the tumor. Some patients with small cell lung cancer are sensitive to chemotherapy even if they have advanced disease and severe symptoms, so they can expect to have a better recent outcome if they are treated with systemic chemotherapy. In contrast, patients with adenocarcinoma who present with similar symptoms often have poor outcomes.