DQ stain, medium power:
Alveolar casts with numerous negatively staining organisms
Smaller than lymphocyte nucleus in background
Note blue dots reflective of trophozoites
DQ stain, high power:
Negatively staining yeast with numerous blue dots suggestive of trophozoites
Pap stain, high power:
Extracellular negatively staining organisms within alveolar cast
GMS stain, high power:
Non-budding organisms with thin wall and dark center
Note there is not much size variation
GMS stain, high power:
Organisms in groups
Note dark centers and lack of budding
Features
• Bronchioloalveolar lavage or washing
• Lung FNA
• Pneumocystis jirovecii
• Predominant form: Yeast-like
• Size: Approximately the size of small lymphocyte nucleus or RBC
• Location: Predominantly extracellular, within proteinaceous casts
• Features:
Almost always present in groups
• DQ stain: Negative images with blue dots (trophozoites)
• Pap stain: Foamy alveolar casts with negatively staining groups
• GMS stain: Thin wall, central dark zone (look like saucers)
• Absence of budding (important to distinguish from Histoplasma)