The Diagnostic Value of Autofluorescence in Hematoxylin-Eosin-Stained Sections for Cutaneous Sporotrichosis.

BACKGROUND

Previous studies suggest that autofluorescence of pathogenic fungi in hematoxylin-eosin (HE) stained sections under ultraviolet (UV) light may offer rapid screening for fungal infections.

AIMS: To evaluate the diagnostic utility of autofluorescence in HE-stained sections for cutaneous sporotrichosis and compare it with Periodic acid-Schiff (PAS) and Gomori's methenamine silver (GMS) staining.

METHODS

A retrospective analysis included 49 fungal culture-confirmed sporotrichosis cases and eight chromoblastomycosis controls from 2022 to 2024. HE-, PAS-, and GMS-stained sections were examined. Autofluorescence in HE-stained sections was assessed using fluorescent microscopy at UV light mode (340-380 nm).

RESULTS

Most patients presented with fixed cutaneous lesions (65.31%, n = 32), predominantly on the upper extremities (73.47%, n = 36). Histologically, suppurative granuloma (55.10%, n = 27) was the most common pattern. Autofluorescence revealed Sporothrix spores with peripheral green-yellow fluorescence against an olive-yellow background, though erythrocyte interference limited detection in hemorrhagic areas. Only 12/49 cases (24.5%) were autofluorescence-positive, all of which were also PAS- or GMS-positive. Sensitivity was significantly lower than PAS (34.7%, p* = 0.063) and GMS (38.8%, p* = 0.021). No false positive occurred in chromoblastomycosis controls. Interobserver agreement was near-perfect (κ = 0.91).

CONCLUSION

Autofluorescence enables rapid Sporothrix detection with perfect specificity and excellent interobserver agreement, but its low sensitivity limits standalone use. PAS and GMS remain superior for definitive diagnosis. While its reagent-free, cost-effective nature supports adjunct screening where special stains are unavailable, erythrocyte interference and technical variability require protocol optimization.