[Two cases of inflammatory pseudotumor of the lung]

Two cases of inflammatory pseudotumor of the lung were reported. Case 1. A 68 year-old man was referred to our hospital because of an abnormal shadow on chest X-ray. He had a history of pneumonia in the right upper lobe five months before. The chest X-ray film revealed a coin lesion in the right upper lung field (S1), the same segment as the previous pneumonia. Although RPF and INH were administered for three months, the shadow did not change, and cough and sputum continued. In order to confirm the diagnosis, open thoracotomy was performed and microscopic findings of the resected tumor showed inflammatory pseudotumor; proliferation of fibrous tissue with infiltration by inflammatory cells (plasma cells, lymphocytes and a few neutrophils). Case 2. A 35 year-old man was admitted to our hospital because of an abnormal shadow on chest X-ray, i.e. a coin lesion with vascular indentation in the left lower lung field (S8). A wedge resection including the mass was performed, and histopathologic examination revealed inflammatory pseudotumor, or plasma cell granuloma; proliferation of fibrous connective tissue with infiltration by predominantly mature plasma cells. Both patients have been doing well after the operation. We also reviewed 46 cases reported in the Japanese literature and discussed various aspects of this disease. Of 10 patients who had a history of previous respiratory tract infection, 8 had histopathologic features with various inflammatory cells, including many lymphocytes, as in our Case 1. Although the common etiology of inflammatory pseudotumor is obscure, we suppose that in some cases the lesion may be a result of post-inflammatory repair process.