Epidermal growth factor receptor (EGFR) immunoreactivity in pulmonary vessels in SScPAH, IPAH and PVOD. (Original magnification 200×). A) EGFR expression of alveolar epithelium surrounding a parenchymal arteriole (corner vessel) in a SScPAH patient, showing weak immunoreactivity of the media and endothelium. B) Weak EGFR immunoreactivity of endothelial cells in a SScPAH patient. C) EGFR expression in media and fibrotic intimal layer of an axial artery of a SScPAH patient. Left lower quadrant: parent artery. Center: glomeruloid lesion, surrounded by dilatation lesions (original magnification 100×). D) Plexiform lesion in an IPAH patient showing weak stromal EFGR expression.