A wide variety of terms have been used for these tumors including histiocytoma, fibrous histiocytoma, fibroxanthoma, xanthogranuloma, plasma cell granuloma, postinflammatory pseudotumor, fibrous xanthoma, xanthomatous pseudotumor, pseudotumor, inflammatory myofibroblastic tumor, and organizing pneumonia. The most common symptoms include cough, hemoptysis, and dyspnea. Chest radiographs typically show a solitary round or oval mass. IPT may also appear as ill-defined areas resembling atelectasis or pneumonia. Most IPT are solitary circumscribed masses.
Most tumors are peripheral.
Both patterns may be present in the same tumor. However, there is a spectrum of histologic features with varying numbers of fibroblasts, histiocytes and plasma cells. Fibroblast predominant lesions may have a storiform pattern. Cytoplasmic immunoglobulin accumulation may produce Russell bodies. Histiocytes are a frequent component and when they show abundant foamy cytoplasm a xanthomatous appearance may result.