PMC6370562_01
HRCT of the patient. Subpleural consolidation associated with pleural thickening (A) and mosaic attenuation (arrows) (B).
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Chest high-resolution computed tomography (HRCT) showed pleural and subpleural thickening with severe fibrotic changes in the marginal parenchyma, flat chest, mosaic perfusion, and reticular shadows in both lungs, added by pneumomediastinum (Fig. 1).
Histological and immunohistochemical findings (A) Area of PPFE showing markedly thickened pleura and subpleural fibroelastosis. (B) Elastica van Gieson staining of the same field shows the increase of elastic fibers. (C-D) Area of BO shows constrictive change by collagenous fibrosis. Note denudation of covering epithelia. (E) Diffuse cellular infiltrates showing NSIP pattern. (F) The transitional area between PPFE and adjacent lung shows denudation and inflammatory cells infiltration into epithelial lining cells creating lymphoepithelial lesions (arrow). (G) AE1/AE3 immunostaining highlights denuded lining epithelia (arrowheads). (H-K). Immunostaining for CD20 (H, J) and CD3 (I, K) reveals almost exclusive CD3 positive cells in NSIP (H, I) and PPFE (J, K). Hematoxylin and eosin (A, C, E, F), elastica van Gieson (B, D), immunohistochemistry (G-K); x 50 (A, B), x 400 (C, D, F, G-I), x 100 (E, J, K).
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Microscopically, subpleural and peribronchial fibroelastosis (Fig. 2A and B), constrictive bronchiolitis (Fig. 2C and D) and cellular and fibrotic non-specific interstitial pneumonia (NSIP pattern) (Fig. 2E) were found. Immunohistochemistry revealed that cellular infiltrates were almost exclusively made of CD3-positive cells with just a few occasional CD20-positive cells (Fig. 2H-K). These inflammatory cells permeated into both alveolar and bronchial epithelial lining cells creating lymphoepithelial lesions (LELs) and erosions (Fig. 2F). AE1/AE3 immunostaining confirmed multiple foci of alveolar cell denudation (Fig. 2G).