[Primary malignant fibrous histiocytoma of the lung]

A chance finding of a sheet-like, dorsal opacification in the left lower lung field of a 77-year-old nonsmoking woman was at first misdiagnosed as tuberculosis because mycobacteria were demonstrated in bronchial secretion. Before it was shown that they were atypical mycobacteria, only facultatively pathogenic, tuberculostatic treatment was started. But both radiologically and clinically the patient's condition deteriorated, with fever and enlargement of the pulmonary lesion. The left lower lobe was resected on suspicion of a chronic pneumonia with consolidation and ultimately abscess formation. The preliminary histological diagnosis of the resected lobe was of a small-cell bronchial carcinoma, stage pT3N0Mx. Further immunohistochemical tests, however, revealed a malignant fibrous histiocytoma which is extremely rare in the lung.