© 2007 American Thoracic Society
Is Giant Cell Interstitial Pneumonitis Synonymous with Hard Metal Lung Disease?From the Authors:We appreciate Dr. Blanc's comments on our article (1). We screened 85 biopsies; tungsten was detected in surgical biopsies from 17 patients and in transbronchial biopsies (TBBs) from three additional patients. Three TBBs were excluded from our study because the pathologists could not make an accurate pathologic diagnosis due to the small size of the TBB. A TBB from an office sweeper without an exposure history was pathologically diagnosed as giant cell interstitial pneumonia (GIP) (2), but we did not include TBB cases. Even though pathologists find giant cells when screening biopsies, they should be careful in making a final diagnosis of GIP, because giant cells are found in other diseases such as viral pneumonia, especially pneumonia due to measles, and sarcoidosis. We applied an improved technique for element analysis of tissue sections using an electron probe microanalyzer (EPMA) with a wavelength dispersive spectrometer (WDS) (1). This technique has about 10 times higher sensitivity than EPMA with an energy dispersive spectrometer and enabled us to detect tungsten in lung tissue in which the element was not found by the other method (unpublished data; Reference 3). We found two biopsies exhibiting features of GIP with neither tungsten nor cobalt detected in the lung tissue by EPMA-WDS nor a working history in the hard metal industry. Finally, 2 (10.5%) of 19 surgical lung biopsies were thought to be "idiopathic" GIP in our case series. In addition to EPMA, atomic absorption spectrometry, plasma optical emission mass spectrometry, and ionic coupled plasma emission spectrometry have been used to detect tungsten and cobalt in lung tissue (2, 4, 5). All of these techniques are methods to detect elements in dissolved tissue solution. Using these methods, one cannot see the relationship between elements and the characteristic lesions of GIP, including centrilobular fibrosis and giant cell accumulation within alveolar space; thus, some GIP diagnosed as hard metal lung disease might actually be "idiopathic" GIP. We agree with Dr. Blanc that "it may have been premature to banish GIP from the schema of ‘idiopathic interstitial pneumonias’" as was done in the 2002 American Thoracic Society/European Respiratory Society statement (6). When we screened lung tissue from patients with suspected occupational lung diseases by EPMA-WDS, we sometimes found elements that have not been thought to cause lung injury, including indium, vanadium, and niobium (unpublished data). "Idiopathic" GIP might be caused by extrinsic elements which are difficult to detect with current techniques.
Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan FOOTNOTES Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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