Nonspecific interstitial pneumonitis (NSIP)

Representative fields of a lung biopsy specimen from a child with NSIP. A low-power view of the lung biopsy specimen (top) demonstrates a mixed pattern of inflammation and fibrosis, with moderately dilated and tortuous air spaces. The high-power view (bottom) demonstrates a mixed inflammatory infiltrate of lymphocytes, histiocytes, and plasma cells, as well as regions of brightly eosinophilic material within the alveolar septae. Patchy intraalveolar macrophages are visible within the air spaces. The alveolar walls are variably thickened by collagen bundles, fibroblasts, and epithelial hyperplasia.