Scanning and transmission electron microscopic study of human pulmonary pneumocystosis.

Histopathologic examinations were performed in 13 autopsy cases with Pneumocystis pneumonia, five of whom were examined with scanning as well as transmission electron microscope. Findings by scanning electron microscopy were compared with those by light microscopy and transmission electron microscopy. By scanning electron microscopy, two principal structural varieties of Pneumocystis organisms, smooth-surfaced organisms and rough-surfaced organisms, could be classified. It was indicated that rough-surfaced organisms and smooth-surfaced organisms correspond respectively to trophozoite-type organisms and thick-walled cysts, recognized with transmission electron microscope. Intraalveolar honeycombed material was mainly composed of dilated trophozoite-type organisms, containing thick-walled cysts scatteredly.