Pneumonia pseudotumor is a benign mass in the lung, formed by granulomas, organization, fibrous connective tissue hyperplasia, and related secondary lesions resulting from chronic inflammation in the lung, and is not a true tumor. Pneumonia pseudotumor is relatively common.

bubble_chart Pathological Changes

The pathological characteristics of inflammatory pseudotumors of the lung are histological pleomorphism. The mass contains varying amounts of granulation tissue, fibroblasts arranged in cords, plasma cells, lymphocytes, histiocytes, epithelial cells, and foam cells or pseudoxanthoma cells containing neutral fat and cholesterol. Therefore, many authors have designated different names and types based on the predominance of certain cells, such as pseudopapilloma type, fibrous histiocytoma type, plasmocytoma type, pseudolymphoma type, etc. The etiology and mechanism of disease are still unclear.

Inflammatory pseudotumors of the lung are generally located within the lung parenchyma, with only a minority involving the bronchi. The vast majority are solitary, presenting as round or oval nodules, usually without a complete membrane, but the mass is relatively localized with clear boundaries. Some are separated from the lung parenchyma by thick, acellular collagenous fibrous connective tissue.

A small number of inflammatory pseudotumors of the lung can undergo malignant transformation.

bubble_chart Clinical Manifestations

Most patients with inflammatory pseudotumors of the lung are under the age of 50, with a higher prevalence in females than in males. One-third of the patients have no clinical symptoms and are only incidentally discovered during X-ray examinations. Two-thirds of the patients have a history of chronic bronchitis, pneumonia, or lung abscess, along with corresponding clinical symptoms such as cough, sputum production, and low-grade fever. Some patients may also experience chest pain, bloody sputum, or even hemoptysis, although the amount of hemoptysis is generally small.

The diagnosis of inflammatory pseudotumor of the lung poses certain difficulties, as the clinical symptoms of patients are often challenging to distinguish from chronic bronchitis and malignant lung tumors. Chest X-ray examinations reveal nodular shadows that are round or oval with smooth, sharp edges, though some edges may appear blurred, resembling spiculation or lobulation, making it difficult to differentiate from lung cancer. Inflammatory pseudotumors of the lung do not have a specific predilection site within the lungs and can range in size from 1cm to 16cm, with most being less than 4cm. These factors contribute to the diagnostic challenges.

bubble_chart Treatment Measures

Since inflammatory pseudotumors of the lung are difficult to diagnose preoperatively, especially distinguishing them from lung cancer, and there is a potential for malignant transformation, early surgical intervention is generally recommended. During surgery, a preliminary diagnosis can be made based on the findings, and if necessary, a frozen section pathological examination can be conducted to confirm the diagnosis. Once the benign nature is confirmed, the principle of the surgery is to preserve as much normal lung tissue as possible. Inflammatory pseudotumors located on the surface of the lung can be easily excised. For those located within the lung parenchyma, a local wedge resection or segmental resection is usually performed. Except for large masses or those that have invaded the bronchi, lobectomy or pneumonectomy is generally not performed. The surgical prognosis is favorable.