The diagnostic value of fungal autofluorescence.

Many pathogenic and saprophytic fungi fluoresce under ultraviolet light. Autofluorescence usually persists even if the specimen has undergone fixation, paraffin embedding, and staining with hematoxylin and eosin. Thus, fluorescence microscopy can help to identify organisms in histopathologic sections of ocular and periocular tissue. It may reveal microorganisms that do not stain with hematoxylin and eosin, and it does not alter or adversely affect microscopic sections. We describe a case of periocular cutaneous blastomycosis which was misdiagnosed clinically and histologically as squamous cell carcinoma. Fluorescence microscopy of the initial hematoxylin and eosin stained section revealed microorganisms that were not appreciated on the first skin biopsy.