Whole‐lung pathology of pleuroparenchymal fibroelastosis (PPFE) in an explanted lung: Significance of elastic fiber‐rich, non‐specific interstitial pneumonia‐like change in chemotherapy‐related PPFE

Pleuroparenchymal fibroelastosis (PPFE) is characterized by upper lobe-predominant subpleural fibroelastosis. Despite its characteristic uneven distribution, detailed whole-lung pathological features of PPFE have rarely been studied. We investigated PPFE in the explanted lungs from a 19-year-old male patient with a history of chemotherapy. Grossly, the explanted lungs showed upper lobe-predominant shrinkage with subpleural and central consolidation. Histologically, fibroelastosis was prominent in the perilobular areas and along the bronchovascular bundles. The other areas of the lung showed diffuse, non-specific interstitial pneumonia (NSIP)-like change with a characteristic increase of septal elastic fibers. In the digital image analysis, the ratio of elastic fibers to whole fibrosis (EF score) was lower in the subpleural areas than in the NSIP-like lesions, but the EF scores of the latter showed no significant difference between upper and middle/lower lobes. In the present case, the diffusely distributed elastic fiber-rich NSIP-like change, probably caused by the earlier chemotherapy, may have been conducive to the development of PPFE. This suggests that some unknown vulnerability of the upper lobe may exist, various primary lesions converging to the upper lobe predominance of PPFE.