I. Diagnosis of pleural diseases: Pleural effusion: The diagnosis of unexplained pleural effusion has been a clinical problem for internists. Because of the large amount of pleural fluid, chest x-ray examination can not determine the site of pleural disease, and make pleural puncture biopsy has a certain degree of blindness, resulting in a positive detection rate is not high. Bacteriologic or cytologic examination of pleural fluid specimens also often fails to make a diagnosis due to lack of specificity. Thoracoscopic surgery allows direct observation of the nature and extent of pleural lesions while obtaining a large number of pleural fluid specimens, and some or all pleural lesions can be removed and sent for pathologic examination. The diagnostic rate of pleural effusion has been significantly improved. In addition, in lung cancer patients with pleural effusion, the presence of pleural metastasis cannot be diagnosed before surgery, and before open-heart surgery, it can be explored by thoracoscopy, which avoids unnecessary surgical trauma caused by blind opening of the chest. In patients with repeated episodes of pleural effusion, which are prone to form single or multiple confined encapsulated effusions, diagnostic thoracoscopic surgery can not only collect a large number of pleural fluid specimens to be sent for examination and increase the rate of diagnosis, but also loosen the pleural adhesions and improve the drainage of the thoracic cavity to achieve the therapeutic purpose. Pleural space-occupying lesions: in patients with pleural space-occupying lesions not accompanied by pleural fluid, although chest x-ray examination can clarify the location of the lesion, it is impossible to determine the nature of the lesion. Even pleural puncture biopsy fails in diagnosis because too little tissue is cut. Thoracoscopic surgery in the direct observation of the lesion at the same time cut enough tissue specimens, can obtain accurate pathological diagnosis, which is particularly valuable in the suspicion of pleural mesothelioma patients to confirm the diagnosis. Diagnosis of lung diseases: With the improvement of surgical techniques and the emergence of a new generation of tissue suturing and cutting instruments, thoracoscopic surgery has become the safest and most reliable diagnostic method for diffuse substantial lung diseases. For patients with diffuse lung lesions, because the lesions severely impair lung function; open lung biopsy is dangerous, with a high incidence of perioperative comorbidities, even resulting in patient death. Thoracoscopic surgery is mildly invasive, and if an automatic endoscopic tissue suture cutter is used, the surgical operation can be completed in a very short period of time, which increases the safety of the operation and leads to a significant decrease in postoperative comorbidities. We report that the simple and easy method of ligating and cutting lung tissue biopsies with a homemade simple endoscopic knot tyer can achieve the same diagnostic results. Nodular lesions on the lung surface can be observed directly by thoracoscopy and can be excised and sent for examination by laser, electric knife or endoscopic tissue auto-stitch cutter to obtain a clear diagnosis. Intrapulmonary metastatic tumors, commonly seen in patients with choriocarcinoma, breast pain, colon cancer and osteosarcoma, are usually multiple. Thoracoscopic surgery can make a clear diagnosis. In case of isolated metastatic foci, local excision of appropriate extent can also achieve better therapeutic results and avoid open-heart surgery. Thoracoscopic surgery is well suited for the diagnostic resection of lesions located on the surface of the lung, especially at the margins of lobar fissures. When the lesion is located deep in the lung tissue or when the lesion appears to be an infiltrative lesion without forming a well-defined mass, it is not easily accessible intraoperatively. A metal wire can be inserted into the center of the lesion under CT or X-ray guidance before surgery. During the operation, the lesion can be found along the metal wire, and the diseased lung tissue can be resected with the wire stabbed into the lung tissue as the center, which increases the accuracy of lung tissue biopsy and improves the diagnosis rate. III.Diagnosis of mediastinal tumor: Although many mediastinal tumors are diagnosed and resected at the same time as open thoracic surgery, preoperative thoracoscopic exploration is necessary in some cases. For example, to determine the relationship between the tumor and the surrounding tissues and organs, and whether it can be surgically resected. Thoracoscopic exploration can reduce the rate of open thoracic exploration. For high-risk patients who are considered to be unable to tolerate open-heart surgery, a definitive pathologic diagnosis is needed to choose a non-surgical treatment method. Thoracoscopic surgery allows easier excision of tumor tissue to obtain a diagnosis. Especially in patients with suspected mediastinal lymphoma, obtaining a detailed cytologic diagnosis and staging prior to treatment is essential for the decision to proceed with radiotherapy and/or chemotherapy. Tumor puncture biopsy, on the other hand, can hardly serve this purpose. Diagnosis of pericardial disease: Thoracoscopic surgery can provide excellent visualization of lesions in the middle mediastinum, allowing pericardial biopsy to be performed and avoiding damage to surrounding structures. Most of the pericardium can be visualized through thoracoscopy, offering the possibility of biopsy in any area of the pericardium. Thoracoscopy is a reliable method of obtaining an effusion specimen, especially in patients with limited pericardial effusions who have failed multiple previous puncture attempts. Excision of small pieces of pericardial tissue not only serves the purpose of cytologic examination of pericardial tissue as well as pericardial effusion, but also serves the therapeutic purpose of pericardial opening and drainage. V. Diagnosis of thoracic trauma Most thoracic trauma can be diagnosed by chest X-ray or thoracentesis. However, such as progressive hemothorax, tracheobronchial rupture and esophageal laceration and other serious thoracic trauma requiring immediate open heart surgery are often difficult to determine by the above examination. Conservative treatment may lose the best time for surgery. Thoracoscopic surgical exploration can clearly diagnose the location and degree of trauma, and decide whether open thoracic surgery is needed, which is an effective method to diagnose thoracic trauma. Tumor staging: Thoracoscopy is also one of the reliable methods for staging chest tumors. In the past, mediastinoscopy was regarded as the gold standard for preoperative staging of lung cancer and was routinely applied in some hospitals. However, mediastinoscopy cannot fully reflect the extent of mediastinal lymphatic metastasis. For example, subglottic lymph nodes, main pulmonary artery window lymph nodes and para-aortic lymph nodes are often difficult to be detected by mediastinoscopy. Thoracoscopic surgery is an excellent way to biopsy mediastinal lymph nodes. In addition, the spread of lung cancer or esophageal cancer to neighboring mediastinal organs or chest wall can be observed through thoracoscopy. It can determine the possibility of tumor resection and avoid unnecessary open chest exploration. (I) Indications used for treatment ① Pleural lesions Malignant pleural fluid: malignant pleural fluid is a clinical manifestation of pleural metastasis of advanced tumors. Rapidly growing pleural fluid often leads to severe respiratory distress in patients. In the past, the methods of injecting chemotherapeutic drugs into the thoracic cavity to reduce the pleural fluid or to promote the adhesion and atresia of the pleura are often ineffective. Thoracoscopic surgery allows the pleural fluid to be aspirated and the adhesions to be separated sufficiently to reopen the lung. Sterilized talcum powder is then sprayed in for pleural fixation, controlling the production of pleural fluid and relieving clinical symptoms in patients with advanced tumors. Acute pyothorax: Braimbridge et al. reported the use of thoracoscopy for debridement and lavage to treat acute pyothorax. Also, fibrous membrane debridement of the lung surface can be performed thoracoscopically to completely expand the lung, eliminate the residual cavity, and accelerate the healing of pyothorax. Pleural tumor: including metastatic pleural tumor, pleural mesothelioma and so on. If the lesion is more limited, it can be completely resected by thoracoscopy to achieve the therapeutic purpose. If the lesion is more diffuse, or the tumor is infiltrative growth, thoracoscopy can not be complete resection, and should be transferred to open thoracic surgery. Spontaneous pneumothorax: Spontaneous pneumothorax is mostly caused by rupture of alveoli, Inderbitzi et al. reported that the recurrence rate of spontaneous pneumothorax was 29% after conservative medical treatment, and 21% after closed thoracic drainage, of which 70% recurred within 2 years. The recurrence rate of open heart surgery is less than 5%. However, patients are often reluctant to undergo open thoracic surgery because it is so traumatic. Thoracoscopic surgery can achieve the same therapeutic effect as open thoracic surgery. Therefore, it is one of the most common diseases for which thoracoscopic surgery is performed. We believe that thoracoscopic surgery should be considered in the following cases: recurrent unilateral spontaneous pneumothorax. Those with persistent air leakage (more than 7 days) after closed thoracic drainage. Bilateral spontaneous pneumothorax, whether simultaneous or not. Those with large pulmonary alveoli that compress the lung tissue and affect the patient’s respiratory function. Benign lung lesions: refers to common benign tumors or foci in the lungs, such as adenomas, misshapen tumors, inflammatory pseudotumors, tuberculous tumors, and bronchiectasis. Conventional treatment is open lung wedge resection or lobectomy. Thoracoscopic surgery is the better option. Since the lesion is often not diagnosed before surgery, the lung tumor can be resected first and sent for rapid frozen pathology. If the tumor is malignant, i.e., intraoperative conversion to open thoracotomy and standard radical surgery. Lung metastatic tumor: according to the patient’s history and symptoms, the diagnosis of lung metastatic tumor is not difficult. For solitary lung metastatic tumor, lung wedge resection or lobectomy can be performed thoracoscopically. Multiple metastatic tumors should be considered for non-surgical treatment. Therefore, preoperative chest CT examination should be routinely performed. Determine the site and number of tumors. Primary lung cancer: thoracoscopic surgery for primary lung cancer is more controversial. In our opinion, in peripheral lung cancer patients with poor idle heart and lung function, who cannot tolerate open thoracic surgery, palliative tumor resection via thoracoscopy, supplemented with radiotherapy and/or chemotherapy after surgery, is not a bad choice of treatment for such patients. If the patient’s condition permits, standard radical surgery should still be performed in order to obtain better long-term results, and Mckenna et al. (1994) reported that lobectomy or total pneumonectomy including mediastinal lymph node dissection was performed to treat the early stage of primary lung cancer, suggesting that the feasibility of thoracoscopic surgery in the treatment of early-stage lung cancer is still to be observed. The clinical therapeutic effect has to be further observed. ③ Pericardial diseases Pericardial tamponade: Pericardial tamponade can occur after chest trauma or surgery due to intrapericardial hemorrhage. If the patient’s hemodynamic indexes are stable, pericardial opening and decompression and hemostasis via thoracoscopy can be considered. It should be noted that thoracoscopic surgery has a longer preparation time, whereas pericardiocentesis or subxiphoid pericardiotomy provides faster relief of pericardial tamponade symptoms. In addition, it is sometimes difficult to detect and abort intrapericardial hemorrhage with thoracoscopic surgery, so the treatment should be chosen carefully according to the patient’s condition. Pericardial effusion: Pericardial effusion is commonly seen in malignant tumors invading the pericardium, intrapericardial infections, uremia, idiopathic pericardial effusion and so on. If the effect of internal medicine treatment is unsatisfactory, partial pericardiectomy via thoracoscopy can be considered. However, the long-term efficacy needs to be further observed. Mediastinal tumor Mediastinal neurogenic tumor: neurogenic tumor mostly occurs in the posterior mediastinum, and there is no difficulty in revealing and peeling off this part by thoracoscopy, which is a better indication for thoracoscopic surgery. However, chest CT or myelography should be performed routinely before surgery, and if it is a dumbbell-type tumor, it should be open thoracic surgery with the assistance of neurosurgeon. Thymoma: Non-invasive growth of thymoma can be resected by thoracoscopic surgery.Lewis(1987) et al. reported that the recurrence rate of thymoma is 12% within 6 years after resection. Therefore, total thymectomy should be performed to minimize the possibility of recurrence. Thymectomy including anterior mediastinal adipose tissue is required in patients with myasthenia gravis, and thoracoscopic surgery is difficult, so it should be considered carefully. Other benign tumors of the mediastinum: including teratoma, intestinal-derived cysts, bronchogenic cysts, pericardial cysts, etc., can be resected thoracoscopically. Care should be taken during surgery to remove the cyst completely to reduce the chance of postoperative recurrence. ⑤ Esophageal diseases Esophageal smooth muscle tumor: Esophageal smooth muscle tumor mostly grows along one side wall of the esophagus, and it can be removed by thoracoscopic surgery. A few smooth muscle tumors that grow around the esophageal wall should be selected for open-heart surgery. During surgery, damage to the esophageal mucosa should be avoided as much as possible. Once damaged, it should be carefully repaired to avoid the formation of postoperative esophageal fistula. Cardia dystrophy: Pellegrini (1992) and others reported that thoracoscopic myotomy of the lower esophagus was performed to treat cardia dystrophy, confirming the feasibility of this surgical approach. However, it should be chosen with caution because of the high incidence of mucosal tearing and perforation in cases of severe mucosal adhesions. (6) Other diseases of the chest such as thoracic duct ligation, thoracic sympathectomy, diaphragmatic hernia repair, incision and drainage of paravertebral abscesses, etc., where thoracoscopy can provide the necessary visualization and complete the basic surgical operation, can be considered for thoracoscopic surgical treatment. With the continuous updating of television thoracoscopes and surgical instruments, as well as the continuous improvement of surgical operation techniques, the clinical application of thoracoscopic surgery is becoming more and more widespread, and will replace more standard open-heart surgery. However, it should be seen that thoracoscopic surgery has its limitations and cannot yet completely replace open thoracic surgery. Some special intra-thoracic surgical operations cannot be performed thoracoscopically. Like any new technology, in the process of clinical application, experience will be accumulated gradually, and the essence will be extracted from the rough, so that this new technology can be developed healthily.