This 40-year-old female from Arizona presented with a verrucous plaque on her shoulder. She did not have systemic symptoms. Coccidioidomycosis usually is a pulmonary disease, however systemic and primary cutaneous forms do occur. The histopathology shows pseudoepitheliomatous hyperplasia with a deep inflammatory infiltrate, both granulomatous and with abscess formation (not shown in this case). The diagnosis is based on visualization of the large (up to 80 micron) spherules/sporangia, as shown in this case. These are filled with numerous spherical endospores. The sporangia and endospores can be within giant cells or extracellularly. Although visualized on H&E, silver and PAS stains will accentuate the organism. This is a biosafety level III organism. Nothing really mimicks this organism, but the tissue reaction can resemble other fungal infections (blastomycosis).
Histologic sections of skin at high power show a refractile spherical object within the tissue. This object is quite large, thick-walled, and appears associated with a multinucleated giant cell. Small spherical endospores are present within the large sphere. The surrounding dermis contains a mixed inflammatory infiltrate with numerous giant cells.