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The National Institute of Food and Agriculture (NIFA) is a relatively new organization established within the US Department of Agriculture in 2009 as part of the 2008 Farm Bill. Its [...]

A 5-y-old, Piedmontese cow had a 4-mo history of ongoing development of skin masses. This was the only cow affected in a herd of 20 cows. Up to 12, hairless, red-to-black, raised nodules-to-plaques were distributed along the dorsum and tail head. Biopsies were taken for histopathology and ancillary testing. An ulcerated skin section contained dermal infiltrates of eosinophils, plasma cells, neutrophils, macrophages, lymphocytes, and multinucleate giant cells, and pyogranulomas. Fungal hyphae were seen within the dermis, multinucleate giant cells, and pyogranulomas. In pyogranulomas, fungi were surrounded by a Splendore–Hoeppli reaction. Dematiaceous (pigmented) hyphae were rarely observed with H&E-stained and unstained (cleared and mounted) sections, but stained well with a Fontana–Masson stain. Exserohilum mcginnisiiwas identified by fungal culture, followed by PCR assay and sequencing. Exserohilumis a dematiaceous fungus that causes disease in humans and rarely in animals. The use of unstained sections and Fontana–Masson stain are important to demonstrate pigment because dematiaceous fungi have little melanin and appear as hyaline hyphae histologically. PCR assay and sequencing aid in the differentiation and classification of fungal species. To our knowledge, E. mcginnisiidermal granulomas have not been reported previously in cattle.