• Andrew Churg, Joanne L Wright, and Christopher J Ryerson.
• *Departments of Pathology, Vancouver General Hospital and University of British Columbia †Departments of Pathology, St Paul's Hospital and University of British Columbia ‡Department of Medicine and Center for Heart Lung Innovation, University of British Columbia, Vancouver, BC, Canada.
• Am. J. Surg. Pathol. 2017 Oct 1; 41 (10): 1403-1409.

AbstractChronic (fibrotic) hypersensitivity pneumonitis (HP) and fibrosing interstitial pneumonias associated with connective tissue disease (CTD-ILD) can be difficult to distinguish in biopsy specimens. To investigate features that might separate these entities, 2 pathologists blinded to the diagnoses reviewed 16 cases of chronic HP and 12 cases of CTD-ILD. Fifteen predefined parameters were examined by morphometric point counting, analysis/cm of lung tissue, or presence/absence. Germinal centers were present in a minority of patients, but favored a diagnosis of CTD-ILD (7/12 CTD vs. 2/16 HP; odds ratio, 9.80 [95% confidence interval, 1.50-63.4]; P=0.02). The number of lymphoid aggregates/cm (4.4±3.1 vs. 1.4±1.0; P=0.001), volume proportion of plasma cells (0.076±0.058 vs. 0.031±0.023; P=0.031), and plasma cell: lymphocyte ratio (1.03±0.71 vs. 0.35±0.22; P=0.001) were all significantly higher in CTD compared with HP. A diagnosis of HP was more common in the presence of peribronchiolar metaplasia (12/16 HP vs. 4/12 CTD; odds ratio, 6.00 [95% confidence interval, 1.15-31.2]; P=0.033) and in patients with a greater fraction of bronchioles showing peribronchiolar metaplasia (0.41±0.33 vs. 0.16±0.27; P<0.001). Number of fibroblast foci/cm, distribution of fibroblast foci, pattern of fibrosis, presence of giant cells/granulomas, and volume proportion of lymphocytes or eosinophils did not distinguish chronic HP from CTD-ILD. We conclude that no single morphologic measure definitively separates chronic HP from CTD-ILD lung biopsies, but numerous foci of peribronchiolar metaplasia favor HP, while the presence of germinal centers, large numbers of lymphoid aggregates, or a high plasma cell: lymphocyte ratio suggests CTD-ILD. Multidisciplinary discussion is often necessary for accurate classification inthis setting.

16 keywords...

hide…