This 47-year-old man developed a necrotic ulcer with eschar and purpuric borders following immunosuppression for an orthotopic liver transplant for liver failure from Hepatitis C Virus infection. The lesion was biopsied and sent for both histology and cultures. The clinical differential diagnosis included deep fungal infection and ecthyma gangrenosum. The histopathology showed scattered filamentous fungi within the areas of necrosis. The apparent aseptate and ribbon-like nature of the fungus is highly suggestive of zygomycosis (mucor, rhizopus, etc), however, degenerated Aspergillus species can look like this, and thus cultures are necessary for confirmation.
This stunning image is from a calcofluor white preparation in this same patient. It is a fluorescence-based stain which brilliantly highlights fungal forms without sifting through artifact, an often frustrating exercise using a standard KOH prep. The wide-angle branching of ribbon-like hyphae mirrors the morphology seen on H&E sections and is characteristic of the zygomycoses, such as Mucor and Rhizopus species.