Silver stain, Pneumocystis jirovecii

Silver stain of lung tissue from a patient with Pneumocystis jirovecii pneumonia. Left panel: At low magnification (x200), the alveolar spaces are filled with foamy exudate, which contains small darkly staining cyst forms of P. jirovecii. Right panel: At higher magnification (x1000), the cysts of P. jirovecii appear as oval, dark structures against the background.