The Cytological Diagnosis of Pneumocystis Carinii By Fluorescence Microscopy of Papanicolaou Stained Bronchoalveolar Lavage Specimens

In a retrospective and prospective analysis fluorescence microscopy of Papanicolaou stained bronchoalveolar lavage specimens has been applied to the diagnosis of Pneumocystis carinii (PC) in routine cytology. The pneumocysts presented as circular structures of 5 microns in diameter and of brilliant green-yellow fluorescence surrounding two mirror image reniform structures. Fluorescent inclusions of 1-3 microns diameter within the alveolar macrophages could be identified as remnants of pneumocysts by a follow-up of all steps of degradation ending in very small irregular granules. By applying both criteria, i.e. pneumocysts with reniform bodies and degradation inclusions within macrophages, Pneumocystis carinii pneumonitis (PCP) could be detected in 100% of cases. Transbronchial biopsy permitted the correct diagnosis in only 65.2% of cases. Retrospective analysis of slides is possible after a long period as no significant loss of fluorescence occurs after 4 years. Thus fluorescence microscopy permits the diagnosis of Pneumocystis carinii without any additional staining or loss of time.