Cokeromyces recurvatus identified in lung biopsy: case report of a non-pathogenic fungus, highlighting its potential histologic mimics.

We report a case of aspiration in a patient with gastric outlet obstruction due to pancreatic adenocarcinoma, in which three large yeasts were identified on tissue biopsy of the lung infiltrate. The histologic sections of the yeasts showed densely eosinophilic, round to oval, thick-walled structures with frayed borders and intra-cystic bluish inclusions. There was a background of mixed neutrophilic and eosinophilic infiltrate along with focal tissue necrosis. Our initial differential diagnoses included the usual large yeasts such as Cryptococcus, Coccidioides, and Blastomyces. Immunohistochemistry revealed reactivity to the Blastomyces antibody. Mycology studies eventually identified the organism as Cokeromyces recurvatus. Anti-fungal treatment was withheld with spontaneous resolution of the infiltrates. This case demonstrates the importance of using culture to speciate organisms identified on tissue, separating pathogens from non-pathogens and non-living artifacts in order for appropriate management.