Atypical cytomorphologic appearance of Cryptococcus neoformans: a report of five cases

Cryptococcus neoformans is not generally recognized as producing pseudohyphae. Although atypical morphologic forms have been described in the microbiology literature, we believe this is the first complete cytologic report describing this uncommon and unusual cytologic appearance of cryptococcal infection.

In five cases of cryptococcal infection, C neoformans formed chains of budding yeasts, pseudohyphae and germ tube-like structures. The atypical forms of C neoformans were seen in cerebrospinal fluid, imprints and in histopathologic sections from multiple organs from two human immunodeficiency virus (HIV)-positive patients; in pleural fluid from a patient with non-Hodgkin's lymphoma; in crush smears from a stereotactic biopsy of the brain; and in a fine needle aspirate of a lung nodule in two patients with no known risk factors for HIV infection.

Recognition of atypical cytomorphologic variants of C neoformans is important since there are potential diagnostic pitfalls for confusing these atypical-appearing organisms with a Candida-type species or fungal contaminants. Special stains for capsular material and culture can be helpful in making a correct diagnosis.