Combined histochemical stains in the differential diagnosis of Cryptococcus neoformans

Three combinations of histochemical stains were used to study 69 routinely processed tissues containing various "yeast-like" fungal organisms (Cryptococcus neoformans, Blastomyces dermatitidis, Coccidioides immitis, Histoplasma capsulatum, Paracoccidioides brasiliensis, and Candida albicans). Fontana-Masson stain combined either with mucicarmine or Alcian blue produced distinctive staining of C. neoformans (Fontana-Masson-positive wall and mucin-positive capsule) that was not identified in other fungi. The Alcian blue stain combined with periodic acid-Schiff reaction also was useful for fungal classification, because the Alcian blue component reacted with only C. neoformans (capsule) and B. dermatitidis (wall) and the periodic acid-Schiff reaction reacted with the cell wall and body of each fungus. We concluded that the combined histochemical stains used in conjunction with morphologic study of hematoxylin and eosin- and Gomori methenamine silver-stained sections are helpful in the differential diagnosis of yeast-like fungal organisms.