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The diagnosis of fibrotic hypersensitivity pneumonitis (also referred to as chronic hypersensitivity pneumonitis, hereafter called FHP) is frequently a difficult problem, because many of the clinical, radiologic, and pathologic features [...], Context.--There is interest in using transbronchial cryobiopsies (CBs) for the diagnosis of fibrotic (chronic) hypersensitivity pneumonitis (FHP), but with little information in the literature about what features are diagnostic in CBs. Objective.--To determine, using in silico investigation, whether features supporting a diagnosis of FHP in video-assisted thoracoscopic (VATS) biopsies can be identified in CBs. Design.--In silico circular "cryobiopsies," 5.25 mm in diameter (21.6 [mm.sup.2]), were created on the slides of 15 VATS biopsy cases that had been assigned a 60% or greater confident diagnosis of FHP at a specially devised multidisciplinary discussion. Using stratified random sampling, up to 8 "cryobiopsies" per case were analyzed for the presence of giant cells/granulomas or peribronchiolar metaplasia affecting 50% or more of the bronchioles, features that had statistically supported a diagnosis of FHP on the VATS biopsies in the multidisciplinary discussion exercise. Results.--Giant cells/granulomas were detected with very low sensitivities in the "cryobiopsies." Using peribronchiolar metaplasia in 50% or more of bronchioles alone, the sensitivity/specificity for a diagnosis of FHP of 2 "cryobiopsies" compared to the corresponding VATS biopsy was 0.57/0.63; for 4 "cryobiopsies," 0.86/0.75; and for 8 "cryobiopsies," 0.83/0.71. Adding giant cells/ granulomas slightly improved these numbers to 0.63/0.71 for 2 "cryobiopsies"; 1.00/0.86 for 4; and 1.00/0.80 for 8. Conclusions.--In the setting of a multidisciplinary discussion where FHP is part of the differential diagnostic choices, 4 actual CBs with an area of roughly 20 [mm.sup.2] each should have good sensitivity and reasonable specificity for diagnosing FHP using these specific morphologic criteria. doi: 10.5858/arpa.2020-0176-OA

To the Editor.--Although many pulmonologists are adopting transbronchial cryobiopsy, there is a remarkable dearth of information on the specific pathologic features used to diagnose various forms of interstitial lung disease [...]

Many pathologists have never heard of chronic hypersensitivity pneumonitis (CHP), but in the past 15 years, CHP has emerged as an important problem in fibrosing interstitial pneumonias, a problem that [...], Context.--Chronic hypersensitivity pneumonitis (CHP) has emerged from obscurity during the past 15 years and is now recognized as a very common form of fibrosing interstitial pneumonia but one that is frequently misdiagnosed both clinically and on surgical lung biopsy as usual interstitial pneumonia/idiopathic pulmonary fibrosis (UIP/ IPF) or fibrotic nonspecific interstitial pneumonia.Objective.--To review the pathologic features of CHP.Data Sources.--Clinical, pathology, and radiology literature were used.Conclusions.--Upper lobe-predominant fibrosis and/or air-trapping on computed tomography scan are features of CHP but not UIP/IPF; however, radiologic separation is possible in only about 50% of cases. Morphologically, CHP sometimes mimics UIP/IPF, but CHP often shows isolated foci of peribronchiolar (centrilobular) fibrosis, frequently associated with fibroblast foci, and in CHP, fibrosis may bridge from the centrilobular region to another bronchiole, an interlobular septum, or the pleura ('bridging fibrosis'). This set of findings is uncommon in UIP/IPF. In addition, CHP may produce a picture of fibrotic nonspecific interstitial pneumonia. Although giant cells/granulomas are usually present in subacute hypersensitivity pneumonitis, they are much less frequently found in CHP, and their absence does not contradict the diagnosis. This diagnostic separation is clinically important because CHP is treated differently than UIP/IPF is (immunosuppressive agents versus antifibrotic agents); further, there are some data to suggest that removing the patient from antigen exposure improves outcome, and there is evidence that patients with CHP have a much better survival prognosis after lung transplantation than do patients with UIP/IPF. In most cases, accurate diagnosis of CHP requires consultation among clinicians, radiologists, and pathologists.(Arch Pathol Lab Med. 2018;142:109-119; doi: 10.5858/arpa.2017-0173-RA)

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the developed world, (1) and thus it constitutes a major focus of medical investigation. The pathologic study [...], Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and is the fourth leading cause of death worldwide. There has been significant progress in the pathologic description and pathophysiologic analysis of COPD in the 20th and 21st centuries. We review the history, progression, and significance of pathologic alterations in COPD, including emphysematous changes, airway alterations, and vascular alterations. We also indicate what pathologic features of COPD the practicing pathologist should be describing in standard surgical and autopsy specimens. (Arch Pathol Lab Med. 2016;140:1423-1428; doi: 10.5858/arpa.2015-0455-RS)

The concept of respiratory bronchiolitis/interstitial lung disease (RBILD) was introduced in 1987 by Myers et al (1) as a morphologic explanation for clinical interstitial lung disease (explicitly, in their article, [...], * Context.--The concept of respiratory bronchiolitis/interstitial lung disease (RBILD) was introduced to explain the presence of interstitial lung disease in individuals whose only finding on surgical lung biopsy was smoker's respiratory bronchiolitis (RB). Over time, the diagnostic criteria for RBILD have become progressively more confused. Objective.--To review the diagnostic criteria for RBILD. Design.--The review was based on the literature and personal experience. Conclusions.--The concept of RBILD has changed over time with the recognition that, histologically and radiologically, RB and RBILD are usually indistinguishable. Most authors accept mild alveolar wall fibrosis extending away from the respiratory bronchioles as a part of both RB and RBILD, and occasional cases show quite marked, but probably localized, interstitial fibrosis. What has not been appreciated is that RB is not only an extremely common disease in cigarette smokers but also is ordinarily associated with airflow obstruction. Further, interstitial fibrosis is sometimes found in centrilobular emphysema, and this phenomenon has probably lead to some cases of centrilobular emphysema being misclassified as RB or RBILD. Despite the presence of fibrosis, centrilobular emphysema is still associated with airflow obstruction. We suggest that RBILD be restricted to the clinical setting in which cigarette smokers have a restrictive or mixed obstructive and restrictive functional abnormality, have a marked decrease in diffusing capacity with minimal evidence of airflow obstruction, or have imaging studies showing ground glass opacities/centrilobular nodules plus reticulation and no other lesion besides RB on biopsy to account for these changes. In this setting, the presence of RB-associated interstitial fibrosis probably causes the functional changes. (Arch Pathol Lab Med. 2010;134:27-32)