Giemsa stain, Pneumocystis jirovecii

Giemsa stain of impression smear of lung tissue (x1000). With this stain, the trophozoites of Pneumocystis jirovecii appear as small, reddish oval forms (arrow), while the unstained cysts of P. jirovecii appear as clear haloes. P. jirovecii can also be identified in specimens using fluorescent antibody techniques.