Seven patients with plasma cell granuloma (inflammatory pseudotumor) of the lung, including two with intrabronchial growth: an immunohistochemical and electron microscopic study.

Seven patients (mean age, 50.7 +/- 20.4 years; range 21-77) with plasma cell granuloma (PCG) of the lung are reported. Cough and sputum were the most common presenting symptoms, followed by fever. Elevated erythrocyte sedimentation rate and serum C-reactive protein levels were found in all patients tested. Radiologically, five cases presented as solitary, well-circumscribed masses and two as ill-defined, pneumonia-like densities. One showed focal calcification. No predilection of occurrence was observed in either lobe of the lung. Histologically, the lesions consisted of a proliferation of mature plasma cells and reticulo-endothelial cells supported by a stroma of granulation tissue, with varying degrees of myxoid change or collagenization. Angioinvasion within the lesion was observed in 4 of the 7 cases. Immunohistochemical staining revealed the IgG-predominant polyclonal nature of the plasma cells, indicating a reactive inflammatory process rather than a neoplastic one. Electron microscopy confirmed the benign nature of the plasma cells with fibroblast and myofibroblast proliferation admixed with that of other inflammatory cells.