Histopathology and staining of lung tissue in a patient with Pneumocystis pneumonia

(A) Photomicrograph shows mild alveolar interstitial thickening by a lymphocyte infiltrate and extensive filling of airspaces by finely vacuolated eosinophilic material.
(B) Magnified view of the material in one of the airspaces shows silver positive (black) round or helmet-shaped structures typical of Pneumocystis jirovecii.