Pneumocystis carinii infection of the lung: radiologic and pathologic correlation.

The incidence of Pneumocystis carinii infection of the lung was determined in 100 consecutive autopsies on patients with hematologic malignancies and in a control group of 50 patients with acute myocardial infarction and chronic obstructive pulmonary disease. Thirteen instances of infection were found in the study group and one instance in the control group. Of the 14 patients with P. carinii infection, five were classified as uncomplicated P. carinii pneumonia with typical host response and five had no evidence of any host response to the presence of the organisms. Four cases were impossible to assess because of complicating bacterial, viral, or fungal pneumonia. The five patients with the typical histologic response to the presence of P. carinii organisms all showed diffuse pulmonary densities on the chest radiographs in accordance with the classic descriptions of P. carinii pneumonia. The five without any evidence of host response to the presence of P. carinii organisms showed no evidence of parenchymal disease on chest radiographs. The finding of P. carinii organisms in the lung is not necessarily an indication of clinically significant disease and, from this study, it seems that chest radiography is of considerable importance in determining the significance of such infestation.