Histology is critical but not always for the diagnosis of chronic hypersensitivity pneumonitis

Background: The diagnosis of chronic hypersensitivity pneumonitis (CHP) is often based on the pathology, but evidence is scarce that a pathological diagnosis of CHP may mislead the multidisciplinary diagnosis. Method: We enrolled patients from the consultation case archive whose pathological findings were suggestive of CHP but had a multidisciplinary diagnosis of non-CHP. The histopathological slides were sent to another pathologist, and the ones confirmed with CHP were sent for an additional multidisciplinary discussion (MDD). We examined clinicopathological features of the cases confirmed to be non-CHP through MDD. Results: Among the 243 cases, five were diagnosed as non-CHP through an additional MDD. The most common causes of discrepancy were the presence of strong autoimmune features, a low lymphocyte level in the bronchoalveolar lavage fluid, and a lack of nodular shadow or mosaic attenuation on computed tomography. Conclusions: Cases of suspected CHP on pathology may be determined to be non-CHP through MDD. (C) 2020 The Japanese Respiratory Society. Published by Elsevier B.V. All rights reserved.