Diagnosis of lung cancer is the first requirement for treatment planning. Patients often ask their doctors what disease they have during outpatient visits and hospitalization. What should be the treatment? So, let’s see how clinicians would go about making a complete diagnosis of lung cancer. Zhou Xianmei, Department of Respiratory Medicine, Jiangsu Provincial Hospital of Traditional Chinese Medicine 1. Histopathology diagnosis Histopathology and cytopathology are still the gold standard for confirming lung cancer diagnosis, so obtaining cell and tissue specimens of the lesion becomes an important condition for confirming the diagnosis. Sputum cytology is the easiest, most economical, and noninvasive test with a 50% positive detection rate for lung cancer, but its sensitivity is influenced by the location of the tumor (central lung cancer is diagnosed at a higher rate than peripheral lung cancer), the type of tissue, and the correct sputum specimen collection, as well as by the skill level of the pathologist. The sensitivity of sputum cytology examination is now considered to be 20-30%, and its reliability is 13-82%. Sputum-based cytology examination has greatly improved the sensitivity and reliability of sputum cytology diagnosis, with a reported sensitivity of 97.2%, specificity of 92.9%, and positive predictive value of 93%. Among invasive examinations, fiberoptic bronchoscopy is the most widely used in clinical practice, and is derived from conventional fiberoptic bronchoscopy: transbronchial lung biopsy (TBLB), transbronchial needle aspiration (TBNA), and in combination with endotracheal ultrasound technology, EBUS-TBLB, EBUS-TBNA. conventional fiberoptic bronchoscopy is mainly for central lung cancer, and can be performed in the bronchus TBLB is used for peripheral lung cancer and lung cancer with extensive metastases in the lung. The application of EBUS-TBNA has improved the sensitivity of TBNA, and it has been reported that the sensitivity and correctness of EBUS-TBNA for the diagnosis of unexplained lung masses reached 94.1% and 94.3%, respectively.2. Molecular biology diagnosis Molecular biology diagnosis mainly involves both genes and proteins of tumor cells. levels. Tumor is a genetic mutation disease, and there is also obvious heterogeneity, so the molecular biology method of diagnosis can provide a clearer understanding of the characteristics of tumor and provide a basis for the formulation of individualized tumor treatment. The current tests mainly involve: (1) the expression levels of certain chemotherapeutic drug-related genes, which are related to the sensitivity of tumor cells to chemotherapeutic drugs. For example, the expression level of platinum drug-related gene ERCC1 correlates with the sensitivity of tumor cells to platinum drugs, RRM1 correlates with the efficacy of gemcitabine, TS correlates with the efficacy of pemetrexed, etc. (2) Mutation status of genes correlated with the efficacy of targeted drugs. The mutation status of the driver genes, represented by EGFR gene, becomes the key to the efficacy of molecular targeted drugs. Therefore, the mutation detection of EGFR gene has become an important and necessary part of pre-treatment diagnosis. With the development and improvement of individualized treatment strategies for lung cancer, the content of molecular biology diagnosis of lung cancer will become more and more abundant.3. Imaging diagnosis Imaging diagnosis techniques mainly involve traditional conventional X-ray examination and chest spiral CT examination, as well as the rapidly developing molecular imaging techniques in recent years. Traditional X-ray examination has many technical limitations and cannot meet the early diagnosis and disease assessment of lung cancer, and as a simple and economical examination means, it is more suitable for routine physical examination and as an exclusionary diagnostic technique. PET-CT is a molecular imaging technique that has been widely used in recent years. It takes advantage of the high glucose uptake rate of tumor cells with high metabolism to detect not only the lesions but also the functional characteristics inside the lesions, which can identify the benign and malignant lung lesions. Many current guidelines recommend PET-CT primarily for single intrapulmonary nodules larger than 8 mm. Many previous studies have concluded that the sensitivity and specificity of PET-CT for the differential diagnosis of solitary intrapulmonary nodules (SPN) are 96% and 80%, respectively, and its negative predictive value is 92-96%. The positive predictive value of PET-CT is lower because inflammatory and granulomatous lesions also have a high metabolic activity. 2012 ASCO annual meeting had authors reporting combined analysis results of 80% sensitivity and 69% specificity of PET-CT examination, respectively, and further analysis showed that most of the false positive cases were granulomatous disease. Therefore, as the application becomes more widespread, the evaluation of PET-CT will become more objective.4. Staging of lung cancer A complete diagnosis of lung cancer must include staging, and accurate staging is a guarantee for the formulation of correct treatment strategies. Nowadays, the method of lung cancer staging is still the TNM method (tumor size, lymph node metastasis, distant metastasis), and the means adopted are non-surgical staging methods (non-invasive) and surgical staging methods (invasive), while the integrated use of various techniques helps to improve the accuracy of staging. Non-surgical staging methods mainly rely on imaging: the agreement rate between X-ray chest radiography and surgical staging is 62.6%, and the accuracy rate is 44.8%. General CT relies on the size of lymph nodes to determine the metastasis of lymph nodes, and its sensitivity and specificity are 57.2% and 80.2%. MRI has a sensitivity of 71% and specificity of 84% for the diagnosis of N2 lymph nodes in lung cancer, and PET has a sensitivity and specificity of 94.1% and 79%, respectively. The most sensitive test is PET, but its specificity is close to that of plain CT, which may cause overestimation of the stage and deprive patients of surgery. Therefore, some scholars believe that PET examination cannot replace surgical staging methods, and mediastinoscopy is still needed for further confirmation in PET-positive cases. Mediastinoscopy is currently the most accurate tool, with a sensitivity of 90% and specificity of 100%, while EBUS-TBNA can achieve the same level of accuracy, but is influenced by the level of operation of the tracheoscope operator and the diagnostic ability of the pathologist. Finally, head MRI, bone scan and whole-body PET-CT are also required to detect distant metastases and make accurate lung cancer staging.