Anatomic Pathology: Neuropathology

• Cryptococcal infection of the central nervous system (CNS) can present as meningoencephalitis or cryptococcal abscesses due to hematogenous spread to the CNS, more commonly in immunosuppressed patients.

• The fungus Cryptococcus neoformans is a spherical/oval budding yeast with a thick polysaccharide capsule, which stains with mucin. The yeasts can also be visualized by PAS or methenamine silver impregnation.

• The leptomeningeal inflammation associated with infection is usually scant and can include lymphocytes, plasma cells, eosinophils, and multinucleated giant cells. The fungal organisms can be seen within the giant cells. The fungus can move along the Virchow-Robin spaces to spread into the brain parenchyma.

• Another yeast infection involving the CNS is candidiasis, which usually presents as a late manifestation of systemic candidiasis. The findings include scattered hemorrhagic infarcts due to thrombosed vessels. Budding yeasts and pseudohyphae can be seen in hematoxylin-eosin (H&E), PAS, and Gomori methenamine silver (GMS) preparations.

• Other yeast forms - Histoplasma, Blastomyces,and Coccidiomycosis - can also infect the CNS when systemic infection occurs, but these cases are rare.