What is an isolated small pulmonary nodule? With increased awareness of medical examinations and the use of modern medical equipment such as CT, MR and PET-CT, the chance of finding lung nodules has increased significantly. There are isolated and multiple lung nodules, and multiple nodules can be seen in one or both lungs. Among the isolated lung nodules, lung cancer and benign lung nodules are included. There are small cell and non-small cell carcinomas in lung cancer, and squamous, adenocarcinoma and large cell carcinoma in non-small cell carcinoma. Other tissue types include adenosquamous carcinoma, alveolar cell carcinoma, and a type of adenosquamous carcinoma (carcinoid tumor). Among benign nodules, misfolded tumors, sclerosing hemangiomas, inflammatory pseudotumors, sarcoidosis, nodular disease, and fungal infections are common. Isolated small nodules in the lung are usually referred to as lung nodules with a diameter of 3 cm or less? i.e. lesions within the T1 period in lung cancer. Some data show that among the small isolated lung nodules, about 30% of lesions with a diameter of about 2 cm are benign lesions and about 70% are malignant cancer nodules. However, nodules with a diameter of 5 mm or less are likely to be benign in about 70% of cases. Therefore, when small nodules in the lungs are found on physical examination, it is important to pay attention to its existence, but there is no need to be alarmed. Nodules less than 5 mm can also be detected in chest CT examinations, but because they are too small, their benign and malignant characteristics are not obvious, and it is difficult to determine its nature in various examinations. The features gradually appear when the nodule is about 1 cm in diameter, and the benign and malignant features are more obvious when the diameter is about 2 cm. However, even if the nodule reaches 3 cm in diameter, even after a whole-body PET-CT examination, 5% to 10% of patients cannot be correctly diagnosed as benign or malignant, and the correct diagnosis can only be made after obtaining pathology with the help of invasive examinations. Small malignant pulmonary nodules. Which diseases are most common? Among the malignant pulmonary nodules, adenocarcinoma of the lung is the most common. Because adenocarcinoma of the lung accounts for about 50% of all lung cancers, and the incidence is increasing. Adenocarcinoma is also characterized by earlier hematogenous metastasis than other types of cancer. 80% of patients have lymph node metastasis when the tumor is about 2.5 cm in diameter. Adenocarcinoma is mainly peripheral type with rich blood supply, it also often invades the dirty pleura and forms pleural indentation. Due to the different speed of tumor growth in all directions, lobulation phenomenon and short burr syndrome often occur. Irregular cavities are formed inside the mass due to necrosis, and these are characteristic X-ray manifestations of lung cancer. If the nodule is accompanied by calcification or ventilation signs within the mass shadow, or if the density is lighter and the edges are blurred, it is more likely to be benign. How to diagnose lung nodules? The diagnosis of pulmonary nodules generally relies on CT of the chest with a thick layer of about 1 mm. If the enhanced CT value increases by about 30 to 90 HU, malignancy cannot be ruled out; CT value less than 30 or more than 90 HU is more likely to be benign; PET-CT can understand the metabolic status of the mass in addition to the imaging performance of the nodule; if the SUV value is ≥3.0, malignancy is more likely, but the SUV value of inflammatory masses may be higher than that of lung cancer. For peripheral lesions, CT-guided percutaneous aspiration can obtain a pathological diagnosis of the tumor, but a negative result still cannot completely exclude the possibility of malignancy. For lesions with enlarged mediastinal lymph nodes, fibrinoscopic aspiration biopsy or bronchoscopic ultrasound-guided needle aspiration biopsy, ENBS-TBNA can be performed. other tests include CT tumor angiography? The diagnosis is based on tumor vascular display. The most common and common chest X-ray plain film, which can get information such as chest overview and determine the tumor site. Chest MR examination, also can understand the nature of nodules. Sputum to find exfoliated cells should be included as a routine examination. The doubling time of lung cancer is from 1 to 16 months. If the mass increases significantly within 2 to 3 months, it is more likely to be malignant; if it increases rapidly in less than one month or shrinks significantly after anti-inflammatory treatment, it is more likely to be inflammatory. A mass that has not changed in 2 to 3 years may also increase in size after a few years. Therefore, even benign masses should be followed up with regular checkups. To determine the nature of a small lung nodule, multi-scientific collaboration, multiple medical techniques and equipment are required. Some malignant tumors have elevated cancer indicators in the blood, and some patients may have extra-pulmonary symptoms such as arthralgia, pestle finger, and carcinoid tumors that secrete hormones and cause endocrine disruption. What should be done when lung nodules are found? 1. Follow up and observe. Follow-up observation is the least damaging way to avoid invasive operations such as biopsy or surgery, as well as the potential risks associated with them. Young, non-smoking or imaging data suggesting benign lesions can be considered for observation follow-up, as well as for patients with contraindications to surgery, where performing invasive operations would pose a risk. It is generally accepted that X-ray chest radiographs or chest CT examinations should be performed at the time of follow-up. The interval from the initial examination is 3, 6, 12, or 24 months, with a minimum observation period of 2 years. During the course of observation and follow-up, if there are changes in the lesion, discontinuation of observation should be considered and surgical resection should be performed. Because of the possibility of malignancy and the ensuing psychological burden, and because a definitive diagnosis may not always be obtained with up to 2 years of observation and follow-up, observation and follow-up is sometimes difficult to implement. 2. Surgery. In the past, the surgical management of isolated small pulmonary nodules with an unknown diagnosis was somewhat controversial, and some scholars suggested close follow-up observation because about half of the isolated small pulmonary nodules are benign lesions, and surgical treatment is then performed if malignant manifestations of the lesions occur during the observation process. The data show that? The 5-year survival rate of early lung cancer can be as high as 40-80% after surgery, while once the metastasis of mediastinal lymph nodes occurs, the 5-year survival rate is only about 10-20%. Early detection and timely treatment are the keys to improve the prognosis of lung cancer. Therefore, most scholars now believe that small isolated pulmonary nodules of indistinguishable nature should be treated by active surgery. Even benign nodules have the significance of resection, which can reduce the burden of patients and avoid the possibility of malignant transformation. Thoracoscopy, as a minimally invasive procedure in thoracic surgery, is beneficial for both the diagnosis and treatment of pulmonary nodules. It has the advantages of less trauma, less pain, faster recovery, shorter hospital stay, a few small incisions of 1.5 cm can remove the lesion, and pathological examination can be performed at that time. In the case of malignant lesions, lobectomy and lymph node dissection can be performed at the same time. In this case, only a small incision of about 3-5 cm is needed; if the lesion is benign, only the mass can be removed? The patient’s concerns are allayed. Advice to you? For nodules ≤4mm, if you find a small nodule in your lung on physical examination, please consult thoracic surgery, respiratory medicine or oncology after 1 year to review lung CT. If the nodule is >4mm, do you have a small nodule in your lung found on physical examination? If you find a nodule >4mm, please see a thoracic surgeon, respiratory medicine or oncologist within 1 month to review your lung CT. if you find an increase in nodule diameter and density, immediate surgery is recommended. Nodules >8mm? You have a small nodule in your lung found on physical examination? If the nodule is >8mm, please consult the Department of Thoracic Surgery, Department of Respiratory Medicine or Department of Oncology for positron emission tomography or PET-CT within 1 month. Once the nodules are found to be increasing in diameter and density, immediate surgery is recommended.