OVERVIEW
Pneumatoid pseudotumor is a nonspecific inflammatory proliferative tumor-like lesion of the lung parenchyma, which is a mass formed by granuloma, mechanization, fibrous connective tissue hyperplasia and related secondary lesions produced by chronic inflammation in the lungs, and is not a true tumor. Pneumatoid pseudotumor accounts for the first or second place of benign lung tumors.
Causes
The etiology of pseudotumor pneumoniae is still not clear, it may be due to bacterial or viral infection causing non-specific inflammation, if the inflammatory lesions in the lungs are not cured, it will lead to proliferation and mechanization of the connective tissue, and then confined to form a tumor-like mass. Pneumatoid pseudotumor is composed of various inflammatory cells and mesenchymal tissues, including plasma cells, lymphocytes, histiocytes, mast cells, and spindle-type mesenchymal cells. The number of these different types of cells varies from lesion to lesion, and even the cellular composition varies in different areas of the same lesion.
Pathology
The pathology of pneumonic pseudotumor is characterized by histological pleomorphism, the mass containing granulation tissue in varying abundance, fibroblasts arranged in strips, plasma cells, lymphocytes, histiocytes, epithelial cells, and foamy cells or pseudoxanthoma cells containing neutral fats and cholesterol, which has led many authors to assign different names and types according to the predominance of cellular occupancy, such as pseudopapillary neoplasia, fibrous histiocytoma, plasmacytoma, plasma cell tumor, and pseudoxanthoma. cytoma type, plasmacytoma type, pseudolymphoma type, etc. The aetiology and pathogenesis are unknown.
Pneumatoid pseudotumor is usually located in the lung parenchyma, and only a few of them involve the bronchi. Most of them are solitary and present as round or oval nodules, usually without complete envelope, but the masses are more confined, with clear boundaries, and some of them are separated from the lung parenchyma by thicker collagenous fibrous connective tissue lacking cells. A few pneumonic pseudotumors can become cancerous.
Symptoms
The majority of patients with pseudotumor pneumoniae are under 50 years old, and there are more females than males. 1/3 of the patients do not have clinical symptoms, and they are only found occasionally on X-ray examination. 2/3 of the patients have a history of chronic bronchitis, pneumonia, pulmonary sepsis, and corresponding clinical symptoms, such as cough, sputum, low-grade fever, and in some cases chest pain, bloody sputum, or even hemoptysis, although the amount of hemoptysis is usually small.
The diagnosis of pneumonic pseudotumor is difficult, and the patient’s clinical symptoms are more difficult to distinguish from chronic bronchitis and lung malignant tumors. On chest X-ray, it is a round or oval nodular shadow with smooth and sharp edges, some of which have blurred edges, seem to have burrs or are lobulated, which is difficult to distinguish from lung cancer. Pneumatoid pseudotumor has no clear preferred site in the lung, and the size can be from 1cm to 16cm, most of them are below 4cm. These make the diagnosis difficult.
Examination
1. X-ray examination
Pneumatoid pseudotumor can occur in any part of both lungs. Spherical tumors usually have smooth and sharp edges, with a diameter of 1-4 cm, relatively uniform density and clear surrounding lung fields. Mass-like tumors are usually indistinct and have blurred edges. The density of some lesions is not uniform, such as multiple complications of acute inflammation can cause the “tumor” shadow to expand, and the surrounding area looks like the flaky shadow of inflammatory infiltration. Therefore, whether the edge of pseudotumor is clear or not depends on the pathological changes around the mass. If the border is clear, there is usually a pseudo-envelope around the tumor, and if the lesion is in the acute stage, the pseudotumor shows inflammation around it, and the exudation around the tumor is mostly fuzzy and there is no pseudo-envelope formation.
2.CT examination
CT image shows the interface between pseudotumor and lung very clearly, even if the chest film shows a large patchy or lumpy blurred shadow, it shows a clear block shadow on CT image, and it is easier to find the existence of small cavities, which can be single or multiple, on CT scanning than on chest radiographs. In addition, the thickening and adhesion of the pleura around the mass on CT images is important for the diagnosis of this disease.
3. Fiberoptic bronchoscopy
Fiberoptic bronchoscopy percutaneous lung puncture and intraoperative frozen pathology are of great significance in the diagnosis and differential diagnosis of this disease.
Diagnosis
1. History and symptoms
Most of them have a history of respiratory tract infection, may have no clinical symptoms or intermittent episodes of fever, cough, sputum and other manifestations, and occasionally hemoptysis.
2. Physical examination findings
Most of them have no positive signs. When there is respiratory tract infection, there may be fever and dry or wet rales on lung auscultation.
3. Auxiliary examination
Chest X-ray and CT scan, there is a 1-6cm diameter round or oval isolated block shadow, medium density, uniform texture, edge is not very clear, a few may have pleural adhesion shadow, most of them are in the periphery of the lungs. If the diagnosis is difficult or malignancy cannot be excluded, open chest or transchest wall lung biopsy should be performed.
Differential diagnosis
Pneumatoid pseudotumor is difficult to be differentiated from lung cancer, tuberculoma and malignant tumor, which brings great difficulties in treatment.
1. Lung cancer
Clinically, the most important thing is to differentiate it from lung cancer, which is directly related to the treatment method and the scope of surgical resection. From the medical history, patients with inflammatory pseudotumor are generally younger in age, most of them do not have long-term smoking history, and there is no obvious change in their general condition, they may have transient fever, no persistent blood in sputum, and no extrapulmonary symptoms; from the imaging, inflammatory pseudotumor is generally located in the periphery of the lungs, and it is presented as an isolated mass, or as a multiple foci of varying size, with more uniform density of the mass, and calcification and cavitation, which is rare; most of the cases can see spots around the mass, which is a very important factor to identify lung cancer. In most cases, speckled shadow can be seen around the mass; mediastinal lymph node enlargement does not confirm that the mass is cancer; lung cancer mass is mostly lobulated, with rough and non-smooth edges, non-uniform density, and necrotic area with lower density, which may be related to more active growth of tumor tissues, and it may be accompanied by pleural effusion, and hilar and mediastinal lymph node metastasis is more frequent. Radionuclide imaging is helpful in determining the nature of the mass. Negative results can roughly exclude tumors, but positive patients should be cautious in determining tumors, and false positives can occur in about 10% of patients. Through the above points, the nature of the mass can be roughly determined.
The points of differentiation from lung cancer are:
(1) Pneumatoid pseudotumor has mild or asymptomatic clinical symptoms, whereas lung cancer has obvious symptoms that progressively worsen; (2) Pneumatoid pseudotumor has mild or asymptomatic clinical symptoms.
(2) Pneumatoid pseudotumor has a slow or no growth, while lung cancer has a short doubling time and rapid development.
(3) CT scan can see single or multiple small cavities in the pseudotumor, even with honeycomb-like translucency. The cavity of lung cancer is generally eccentric and thick-walled, with cancer nodules inside the cavity, and rarely shows a honeycomb-like hypodense shadow in one cancerous focus.
(4) Pneumonic pseudotumor is not detected by sputum examination or bronchoscopic biopsy.
2. Tuberculosis ball
Tuberculosis ball is differentiated from tuberculosis ball: tuberculosis ball tends to occur in the apical posterior segment of the upper lobe or the dorsal segment of the lower lobe of the lung, with uniform density, calcification and satellite foci around the lesion. Lung cancer tends to occur in the anterior segment of the upper lobe, and the tumor is lobulated, umbilical concave, short burr and other signs are helpful to distinguish from pseudotumor.
This disease also needs to be differentiated from chronic bronchitis and occupying lesions such as malignant tumors of the lungs, benign tumors of the lungs and pleural mesothelioma.
Treatment
Since pneumatoid pseudotumor is difficult to diagnose before surgery, especially difficult to distinguish from lung cancer, and occasionally has the possibility of cancer, therefore, early surgical treatment is generally advocated. Intraoperative pathological frozen section examination is needed to clarify the diagnosis. After determining the benign nature, the principle of surgery is to preserve normal lung tissue as much as possible. Inflammatory pseudotumor located on the surface of the lung can be resected as a pulmonary wedge. Inflammatory pseudotumor located in the lung parenchyma can be resected by segmental resection or lobectomy. Except for huge masses and those that have invaded the main bronchus, total lung resection is generally not done.