Cytologic features of pulmonary malakoplakia related to Rhodococcus equi in an immunocompromised host.

Cytologic features are described in bronchial brushings of a large cavitary lung mass from an immunosuppressed patient who had undergone liver transplantation. Scattered histiocytes with abundant eosinophilic, vacuolated cytoplasm were noted in a background of bronchial cells. Within approximately one fourth of the histiocytes, targetoid intracytoplasmic inclusions were present, consistent with Michaelis-Gutmann bodies. They were diffusely positive by histo-chemical staining with von Kossa, Gomori methenamine silver, and periodic acid-Schiff stains, and focally positive with Prussian blue stain. Cultures of the abscess yielded Rhodococcus equi. The characteristic microscopic features of pulmonary malakoplakia can be discerned in bronchial brushings, and should be sought, particularly in immunocompromised patients.