Cryptogenic organizing pneumonia: High-power view

Photomicrograph of specimen from open lung biopsy in a patient with cryptogenic organizing pneumonia. A polypoid mass of granulation tissue is filling the lumen of an alveolar duct (Masson body).

High-power photomicrograph shows alveoli containing capillaries within a narrow interstitium. The alveoli are lined with thin, elongated type I pneumocytes (arrow) and smaller numbers of cuboidal type II pneumocytes (dashed arrow).