Which fungal species is most likely identified in tissue stained with mucicarmine highlighting a capsule?

• A. Candida albicans
• B. Cryptococcus neoformans
• C. Aspergillus fumigatus
• D. Histoplasma capsulatum

Answer: (B)

Encapsulated yeasts are highlighted by mucicarmine because the stain binds to the polysaccharide capsule surrounding certain fungi. Cryptococcus neoformans has a prominent mucopolysaccharide capsule, so when tissue is stained with mucicarmine you see a distinct pink-red capsule surrounding the yeast cells. That capsule halo is a key identifying feature of cryptococcal infection in histology.

Candida albicans appears as budding yeasts and sometimes pseudohyphae but generally lacks a true capsule, so there isn’t a capsule to highlight. Aspergillus fumigatus shows hyphae with septa and acute-angle branching, not encapsulated. Histoplasma capsulatum is a small intracellular yeast without a capsule, so mucicarmine wouldn’t outline a capsule around it.