Sensitivity and specificity of immunohistochemistry for the diagnosis of filamentous fungal infections.

OBJECTIVES: Many fungal species share overlapping morphologic features in tissue sections, preventing reliable identification and optimal treatment. We sought to determine whether immunohistochemistry (IHC) using a panel of commercially available antibodies could effectively distinguish between fungi commonly encountered in anatomic pathology specimens. METHODS: Anti-Aspergillus, anti-Rhizopus, and anti-Candida IHC was performed on formalin-fixed, paraffin-embedded tissue sections from 24 cases with fungal infections identified by culture or sequencing (including 4 polyfungal infections). RESULTS: Anti-Aspergillus IHC was positive in 6 of 6 Aspergillus and focally in 1 of 4 Candida species infections and negative in all cases of Fusarium, Scedosporium, Rhizopus, and Mucor species, yielding overall sensitivity of 100% and specificity of 95%. Anti-Rhizopus IHC was positive in 4 of 4 Rhizopus and 1 of 3 Mucor species infections and negative in all other cases, with a sensitivity of 71% and a specificity of 100%. Anti-Candida IHC was positive in 4 of 4 Candida species infections and showed some cross-reactivity in all other cases, resulting in 100% sensitivity and 0% specificity. CONCLUSIONS: Anti-Aspergillus IHC was highly sensitive and specific in its ability to distinguish Aspergillus from other similar-appearing hyaline molds, including Fusarium and Scedosporium species. Anti-Rhizopus IHC was moderately sensitive and highly specific, while anti-Candida IHC was highly sensitive but had minimal specificity.