Lung, radiation pneumonitis

Acute radiation pneumonitis is a typical inflammatory respnse of the alveolar wall seen with any pneumonitis along with epithelial cell necrosis, alveolar hemmorrhage, and the formation of hyaline membranes. As with any long term pneumonitis, pulmonary fibrosis occurs. In this specimen note the large cellular infiltrate of the alveolar wall and the small alveolar air spaces that are lined with hyaline membranes.