Histology of pulmonary lesions. Hematoxylin and eosin stain was used for the lung biopsy, original magnification, 400×. Arrow points to eosinophils with pink color; alveoli are infiltrated with inflammatory cells, mainly eosinophils, lymphocytes and neutrophils. There is no evidence of vasculitis or alveolar hemorrhage. There is some fibrous tissue in the periphery. Note that only distal airways are involved with sparing of proximal airways.