The differential diagnosis of pulmonary granulomatous nodules include, necrotizing sarcoidal granulomatosis, other infectious diseases and tuberculosis, such as nontuberculous mycobacteria, fungal or nematode infection. Wegener granulomatosis, plasma-cell granuloma and lymphoma may also present with multiple pulmonary nodules. Although necrotizing sarcoidal granulomatosis may mimic metastatic lung cancer, multiple, bilateral nodular opacities are not a frequent pattern in pulmonary sarcoidosis. Lung lesions, ie, multiple and cavitary nodular densities, may be the sole manifestation of Wegener granulomatosis. ANCA is negative in approximately 40% of patients with localized Wegener granulomatosis, and ANCA has been reported in various infectious disorders including tuberculosis. The role of neutrophils in the pathophysiology of tuberculosis seems to be minor compared with that of macrophages and T lymphocytes. M tuberculosis can, however, stimulate the release of oxygen metabolites from neutrophils. This activation most likely leads to the release of lysosomal enzymes from neutrophils in the initial stages of the infection, and autoantibodies against the granular components of the cells can develop. In addition, the proteinase-3 expression on the cell surface of activated neutrophils and the release of proteinase-3 on neutrophil degranulation in patients suffering from sepsis provide possible mechanisms for the induction of ANCA production with infection. The role of antituberculosis drugs, especially isoniazid, has also been suggested to explain the production of ANCA in patients with tuberculosis. Plasma-cell granuloma is an heterogenous entity that most commonly involves the lung in adulthood. The lesion mimics a malignant tumor and may occur secondary to infectious diseases, such as mycobacterial infections. However, the histologic analysis of these lesions demonstrates intense inflammation with a predominance of mature lymphocytes and plasma cells that is markedly different from classical epithelioid and giant-cell granulomas.