Anatomic Pathology Board

Practice session

A bronchoalveolar lavage transbronchial biopsy in an immunocompromised patient with bilateral pulmonary infiltrates demonstrates round-to-cup-shaped, 4 to 6 micrometer structures with central dark dots ('crushed ping-pong balls') within alveolar intra-alveolar foamy exudates. Which of the following special stains is the most sensitive for highlighting the carbohydrate-rich cell walls of Pneumocystis jirovecii organisms as sharp black/dark brown structures?

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