Which histologic findings are characteristic of pulmonary alveolar proteinosis (PAP)?

Updated: Dec 18, 2019
  • Author: Roger B Olade, MD, MPH; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

Light microscopy of the lung parenchymal tissue shows alveoli filled with a granular periodic acid-Shiff (PAS) base-reactive and diastase-resistant eosinophilic material.

Pulmonary alveolar proteinosis. Intra-alveolar mat Pulmonary alveolar proteinosis. Intra-alveolar material is strongly periodic acid-Schiff (PAS) positive (diastase-PAS, x200).

Electron microscopy of the material in the alveoli shows multilamellated structures and membranous vesicles. Eosinophilic granular material is present within the alveolar spaces (see the following images). 

Pulmonary alveolar proteinosis. Alveoli are filled Pulmonary alveolar proteinosis. Alveoli are filled with an eosinophilic granular material. Note the preservation of the normal lung architecture (hematoxylin and eosin, x200).
Pulmonary alveolar proteinosis. High magnification Pulmonary alveolar proteinosis. High magnification illustrating the granular material and alveolar macrophages surrounded by intact alveolar septal tissue with minimal reaction (hematoxylin and eosin, x400).

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