Granulomatous lesions can be divided into granulomas with epithelioid cells and granulomas without epithelioid cells according to the presence or absence of epithelioid cells. Granulomas with epithelioid cells with necrotic epithelioid cells are mostly primary infectious lesions, such as tuberculosis and fungal infections. Necrotizing nodular granuloma, central bronchial granuloma, Wegener’s granuloma and necrotizing epithelioid granuloma occurring in rheumatoid arthritis are all infectious granulomas. Granulomas can also be formed without the occurrence of necrotizing epithelioid cells, such as nodular disease and allergic diseases. Inflammatory granulomas formed by bacterial infections are mostly granulomas without epithelioid cells. The differential diagnosis of pathological histology of epithelioid granuloma lesions is sometimes not easy, and the diagnosis is even more difficult via chest wall lung puncture.
(i) Nodular disease is an epithelioid nodule without caseous necrosis that can occur in the lung. The early stage is a mononuclear cell infiltrate of the lung parenchyma, which is a nonspecific alveolitis and further develops into granulomas. Granulomas may be distributed in the lung parenchyma and in the peribronchial and perivascular interstitium. In advanced granulomas, a fibrous envelope is formed around the granuloma, and the peripheral part of the old granuloma produces fibrous tissue with hyaline degeneration. In nodal disease, involvement of hilar and mediastinal lymph nodes is more common than pulmonary involvement, and pathologic changes include cellular infiltration, granulomas, and fibrosis.
(b) Lymphomatoid granuloma is an angiocentric infiltrative granulomatous disease, also known as angiocentric lymphoma. The pathological changes are vascular-centered polymorphic cell infiltration and multifocal necrosis, and the infiltrating cells are mostly small lymphocytes, plasma cells, histiocytes and immune cells.
(C) Inflammatory granuloma Inflammatory granuloma can be formed by bacterial and fungal infections and metaplasia. Granulomas are composed of inflammatory cells, macrophages, and in some cases, epithelioid cells. Exogenous alveolar inflammatory granuloma resembles nodular disease, but differs from nodular disease in that it does not usually involve the hilar and mediastinal lymph nodes.
(iv) Langerhans cell granuloma, also known as eosinophilic granuloma. The early inflammatory lesions of Langerhans granuloma are eosinophilic, lymphocytic, and neutrophilic infiltrates centered in the fine bronchi, and Langerhans cells (Langerhans cells) and alveolar macrophages are seen in the alveolar lumen. The disease often involves small pulmonary arteries and veins. Interstitial fibrosis and small cysts occur in the late stages of the disease, which can involve the lungs and bones.
(E) Wegener’s granulomatosis The basic lesion of Wegener’s granulomatosis is vasculitis and granuloma formation in small arteries and veins. The lesions often involve the bronchi and lungs and are necrotizing granulomas with polyangiitis. The granuloma is infiltrated by epithelioid cells, multinucleated giant cells, plasma cells, lymphocytes, and a few eosinophils. The central part of the granuloma may be necrotic and form a cavity. Bronchial granuloma may cause pulmonary atelectasis. The initial lesions may involve the upper respiratory tract, mainly in the nasal cavity, oral cavity and pharynx.