Plastic embedding evaluation of Pneumocystis carinii pneumonia in AIDS. Simultaneous demonstration of cyst and sporozoite forms.

To study the possible role of plastic embedding in the surgical pathologic diagnosis of Pneumocystis carinii pneumonia, bronchial biopsy specimens from five patients with AIDS were examined using 0.9 micron thick methacrylate sections stained with silver methenamine borate and counterstained with toluidine blue. This technique was found to be superior to paraffin embedding in the demonstration of the fine structural details of both Pneumocystis and the surrounding lung tissue. This method permitted the simultaneous demonstration of both the cyst wall and intracystic sporozoites of Pneumocystis in biopsy tissue, which had been previously possible only by using electron microscopy. This technique assists in the differentiation of Pneumocystis from other opportunistic agents, and may be useful in estimating the relative numbers of cyst and sporozoite forms of the organism. We recommend that bronchoscopic and open lung biopsies from AIDS patients suspected of having Pneumocystis pneumonia be submitted for plastic embedding and high-resolution light microscopy.