Pulmonary inflammatory pseudotumors are relatively common benign masses in the lung, formed by granulomas, mechanization, fibrous connective tissue proliferation and associated secondary lesions arising from chronic inflammation in the lung, and are not true tumors. It often forms a mass within the lung. It is composed of a variety of inflammatory cells and mesenchymal tissue, including plasma cells, lymphocytes, histiocytes, mast cells and spindle-type mesenchymal cells. These different types of cells are present in varying numbers in different lesions and even vary in cellular composition in different areas of the same lesion. Clinically, pneumonic pseudotumors are uncommon and can occur in both men and women. Patients range in age from 1-70 years, but are more common in younger people, mostly in their 30s. Half of the patients are asymptomatic, while the rest may have symptoms related to the lungs and chest, such as cough, hemoptysis, shortness of breath and chest pain. Some of them may have fever. The lesions can occur in any lobe of the lung and often appear as isolated, well-defined round or ovoid masses on X-ray. In larger cases, the mass is ill-defined and occasional calcification or cavity formation is seen. Large solid nodular masses, located in the peripheral parenchyma of the lung, are also seen in the trachea or large bronchi, and some may occupy the entire lobe, sometimes extending into the mediastinum, intrathoracic fascia, or diaphragm. Similar lesions have also occurred in the interlobular fissures. Microscopically, a solid mass with loss of basic lung structures is seen, and at the margins of the mass, the lesion expands into the adjacent interstitium of the lung parenchyma, causing some alveoli or fine bronchi to be scattered among them; alveolar epithelial hyperplasia is evident, and the alveolar septum is occupied by clusters of tumor cells of unknown origin, which may be heterogeneous and divisive. The interstitium is seen to be hyperplastic and hyaline, with the tumor cells showing “infiltrative” growth. The biological behavior of this tumor is benign and can be cured by surgical excision, or can continue to grow if incompletely excised. The prognosis is generally good. The pathology of pneumonic pseudotumor is characterized by histologic pleomorphism, with the mass containing granulation tissue of varying numbers of fibroblasts, plasma cells, lymphocytes, histiocytes, epithelial cells, and foamy or pseudoxanthoma cells containing neutrophilic fat and cholesterol, so many authors have given the mass different names and types depending on the predominance of cells, such as pseudopapillary tumor, fibrous histiocytic tumor, fibrous histiocytic tumor, fibrous histiocytic tumor, and pseudoxanthoma. The pathogenesis and pathogenesis are unknown. The etiology and pathogenesis are still unclear. Pulmonary inflammatory pseudotumors are usually located in the lung parenchyma, and only a minority of them involve the bronchi. Most of them are solitary, round or oval nodules, usually without an intact envelope, but the masses are confined and well-defined, and some of them have thick collagenous fibrous connective tissue without cells separating them from the lung parenchyma. A small number of pneumonic pseudotumors can become cancerous. Clinical manifestations Most patients with inflammatory pseudotumor of the lung are under 50 years of age and more women than men. 1/3 of patients have no clinical symptoms and are detected only occasionally during X-ray examination. 2/3 of patients have a history of chronic bronchitis, pneumonia, pulmonary sepsis, and corresponding clinical symptoms, such as cough, sputum, low-grade fever, and some patients have chest pain, hematochezia, and even hemoptysis, but the amount of hemoptysis is usually small. The diagnosis of inflammatory pseudotumor of the lung is difficult, and the clinical symptoms of patients are more difficult to differentiate from chronic bronchitis and malignant tumors of the lung. On chest X-ray, the nodules are round or oval with smooth and sharp edges, and some of them have blurred edges, appear to have burrs or are lobulated, which are difficult to distinguish from lung cancer. Pulmonary inflammatory pseudotumors do not have a clear site of predilection in the lung and can range in size from 1-16 cm, with most being under 4 cm. All these make the diagnosis difficult. Diagnosis 1.History symptoms Most of them have a history of respiratory tract infection. They may have no clinical symptoms or intermittent episodes of fever, cough and sputum, and occasionally hemoptysis. 2, physical examination findings Most of them have no positive signs. When there is respiratory infection, there may be fever and dry or wet rales on lung auscultation. 3.Auxiliary examination Chest X-ray and CT scan, there are isolated masses with a diameter of 1-6 cm round or oval, medium density, homogeneous texture, the edges are not very clear, a few may have pleural adhesions, mostly in the periphery of the lung. If there is difficulty in diagnosis or malignancy cannot be excluded, open chest or transthoracic lung biopsy should be performed. X-ray examination Pulmonary inflammatory pseudotumor can occur in any part of the two lungs. In this group, there are more pseudotumors in the right upper lung (12/20) than in the left upper lung (2/1 Pneumonia pseudotumor 0), which are mostly located in the dorsal segment of the lower lobe and the inner posterior basal segment. Spherical tumors generally have smooth and sharp margins, are mostly 1-4 cm in diameter, have relatively uniform density, and have clear surrounding lung fields. Mass-like tumors are generally poorly defined and have blurred margins. Some lesions have uneven density, and if they are complicated by acute inflammation several times, the “tumor” shadow may be enlarged and resemble a lamellar shadow of inflammatory infiltration around it. Therefore, the clarity of the margins of the pseudotumor depends on the pathological changes around the mass. If the border surface is clear, there is usually a pseudo envelope around the tumor. If the lesion is in acute stage, the pseudotumor shows inflammation around the tumor, and the exudation is mostly blurred around the tumor and no pseudo envelope is formed. CT scan is easier to detect the presence of small cavities, which can be single or multiple, than chest plain film. In addition, CT images showing thickened pleural adhesions around the mass are important for the diagnosis of this disease. 3.Other examinations Fiberoptic bronchoscopic percutaneous lung aspiration and intraoperative frozen pathological examination are of great importance for the diagnosis and differential diagnosis of this disease.