Histological analysis

Histopathological evaluation was performed using hematoxylin-eosin-stained 5 μm slides from formalin-fixed paraffin-embedded lung obtained during a biopsy or after lung transplantation. Representative sections from each lobe of both lungs were obtained after lung transplantation. Specimens included vascular and bronchial surgical margin, hilar lymph nodes, and five or more representative samples of each lobe. Any remarkable macroscopic finding was included. Pulmonary arteries were evaluated for PAH signs such as medial hypertrophy/hyperplasia, intimal and adventitial fibrosis, and thrombotic lesions, plexiform lesions [23]. PVOD involvement was defined as an extensive and diffuse obstruction of pulmonary veins and venules by intimal thickening, with either fibrosis, cellular proliferation, or muscularization [14, 23]. Samples were also evaluated for the presence of parenchymal lung disease, diffuse developmental disorders, and growth abnormalities [24].