Masson bodies are histologic features most characteristic of which condition?

• A. Cryptogenic organizing pneumonia
• B. Bronchitis
• C. Pneumonia
• D. Emphysema

Answer: (A)

Masson bodies reflect a healing pattern after alveolar injury called organizing pneumonia. In this process, inflammatory exudate in the airspaces reorganizes into granulation tissue that plugs the alveolar ducts and alveoli. These plugs are intraluminal, polyploid-like clusters of fibroblasts and myofibroblasts within a loose connective tissue matrix, often with capillaries—together called Masson bodies. This histology is the hallmark of cryptogenic organizing pneumonia, the idiopathic form of organizing pneumonia. The other conditions listed don’t produce these intra-alveolar fibromyxoid plugs: bronchitis centers on airway inflammation, pneumonia shows acute infectious exudates without organized intra-alveolar plugs, and emphysema features destruction of alveolar walls rather than organizing tissue within airspaces.