Pulmonary alveolar proteinosis revealed by lung biopsy

A previously healthy 40 year-old-man with a recent shortness of breath and bilateral hilar based hazy opacities infiltrations of the lungs on radiology was submitted to a VATS biopsy for differential diagnosis. Microscopic sections of the lung biopsy showed granular eosinophilic acellular, alveolar consolidations with unremarkable alveolar walls. These alveolar secretions were strongly periodic acid-Schiff reaction with diastase (PAS-D) positive revealing their proteinaceous nature distinguishing them from simple transudates (i.e., edematous or inflammatory). This typical diffuse positive reaction with PAS staining is due to accumulation of large amounts of surfactant apoprotein. Methanamine silver stain was negative ruling out Pneumocystis jirovecii and fungal organisms. The patient was diagnosed as having alveolar proteinosis both clinically and pathologically. Although the diagnosis can be made by bronchoalveolar lavage (BAL) yielding a milky fluid, this condition may also be accompanied by tuberculosis, acute silicosis, nickel exposure, and other diseases so having a lung biopsy is beneficial in eliminating additional conditions.