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A2334 - Study of Pathological Features of Lung Lesions in PPFE of Idiopathic or Transplantation Related Cases with Evaluation of the Elastic Fiber Related Conditions Comparing to Those of IPF/UIP
Author Block: Y. Terasaki1, N. Kokuho1, M. Terasaki1, S. Kunugi1, T. Hishima2, Y. Aono3, Y. Nishioka4, T. Kijima5, K. Hashimoto6, K. Ichikado7, A. Shimizu1; 1Department of Analytic Human Pathology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan, 2Department of Pathology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Japan, 3National Hospital Organization Higashi Tokushima Medical Center, Itano, Japan, 4Tokushima Univ, Tokushima 770 8503, Japan, 5Osaka University, Suita, Japan, 6Division of Medical Oncology and Molecular Respirology, Faculty of Medicine Tottori University, Yonago, Japan, 7Division of Respiratory Medicine, Saiseikai Kumamoto Hospital, Kumamoto City, Japan.
RATIONALE Pleuroparenchymal fibroelastosis (PPFE) is now a defined clinicopathologic entity in the updated 2013 ATS/ERS classification of idiopathic interstitial pneumonias, which has led to a significant increase in cases being diagnosed as both idiopathic PPFE or PPFE due to secondary causes and associations, however the etiopathogenesis is still unknown. METHODS We studied the pathological features of lung lesions in 6 cases of idiopathic PPFE (autopsy 1 case, biopsy 5 cases) and 3 cases of bone marrow transplantation-related cases (necropsy 2 cases, biopsy 1case) and compared their differences. We also evaluated the elastic fiber related conditions of them with comparing to those of 8 cases of Idiopathic Pulmonary Fibrosis (IPF)/Usual interstitial pneumonia (UIP). RESULTS All lung lesions of 6 idiopathic PPFE cases showed collapsed and marked elastofibrotic lesions in subpleural and peri-bronchovascular alveolar area associated with findings of early fibrosis lesions, lymphangiogenesis, and infiltration of lymphocytes and eosinocytes in upper lobes. Lung lesions of 3 cases related to bone marrow transplantation also had similar elastofibrotic lesions, but with bronchiolitis obliterans findings, and were also seen in the lower lobes in addition in upper lobes. Lung lesions of 2 cases of them have seen mainly in peri-bronchovascular alveolar area with notable organizing pneumonia findings instead of subpleural alveolar area. In the all lung lesions of 9 PPEF cases, elastic fibers in the alveolar septal walls remained and newly formed elastic fibers were seen in and around the early fibrotic lesions with clear expression of latent TGFβ-binding protein2 (LTBP2), which is important factor as elastogenic organizer. There were cystic lesions on the pleural side continuously formed from the bronchus, and the cyst walls were hyalinized and their inner surfaces were covered by macrophages instead of bronchiolization findings. In the lung lesions of UIP cases, elastic fibers in the alveolar septa tended to disappear and early fibrotic lesions were seen without clear findings of newly formed elastic fiber nor LTBP2 expression. Cyst formation was seen with notable findings of bronchiolization, smooth muscle proliferation and collagen fibers deposition as honeycomb change. CONCLUSION Although clinicopathologic entity of PPFE and IPF/UIP are both refractory and they have both early fibrosis lesions within the lesions, the elastic fiber related conditions in and around early fibrosis lesions may be different between two lesions such as elastic fibrillogenesis or elastolysis thus important for their etiopathogenesis.