RESUMO
BACKGROUND: Sporotrichosis is frequently difficult to diagnose because its morphologic appearance may closely resemble mycobacterial infection or noninfectious inflammatory reaction. Sporothrix schenckii may be difficult to identify in histological sections stained with histochemical staining such as haematoxylin and eosin, periodic-acid-Shiff(PAS) and Gomori's-methenamine-silver (GMS). OBJECTIVE: The purpose of this study was to determine whether immunohistochemical staining with a polyclonal anti-Mycobacterium bovis(BCG) antibody, which is known for its interspecies cross-reactivity between microorganisms, is the suitable screening method to detect Sporothrix schenckii of sporotrichosis in skin tissues. METHODS: Thirty sporotrichosis samples of formalin-fixed, paraffin-embedded skin tissues were stained with anti-BCG immunohistochemical stain (anti-BCG stain) and PAS stain. RESULTS: Thirteen cases (43%) of 30 were positive with PAS stain, and 19 cases (63%) were positive with anti-BCG stain. In 24 cases which were positive in fungal culture, 11 were positive in both stains, 1 was positive in PAS stain only, 6 cases were positive in anti-BCG stain only, and 6 were negative in both stains. In 6 cases which were negative in fungal culture, 1 was positive in both stains, 1 was positive in anti-BCG stain, and 4 were negative in both stains. CONCLUSION: Because of its cross-reactivity with fungi as well as its high sensitivity and minimal background staining, the anti-BCG stain can be the useful screening method of detection of S. schenckii in paraffin-embedded specimens of sporotrichosis.