The biopsy specimen showed pseudoepitheliomatous epidermal hyperplasia overlying a dense inflammatory infiltrate. Some sections showed sulfur granules with colonies of gram-positive rods at the center of microabscesses (Figure 3). The organisms were acid-fast, and there was a positive reaction on periodic acid–Schiff staining. These findings were consistent with actinomycosis, and the tissue culture was positive for N brasiliensis. Sulfamethoxazole-trimethoprim (Septra DS [double strength], twice a day) and dapsone (50 mg twice a day) therapy was begun.
A Draining Tumor in the Popliteal Fossa. Arch Dermatol. 1999;135(8):983–988. doi:10-1001/pubs.Arch Dermatol.-ISSN-0003-987x-135-8-dof0899
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