Sporotrichosis mimicking keratoacanthoma.

A 73-year-old female presented with a tumor in the frontal region, which had been noticed for the last 3 months (Figure 1, Figure 2 ). The patient observed a papule similar to a mosquito bite that grew to become tumoral. Incisional biopsy was performed and the lesion partially regressed over the next 30 days, although not treated (Figure 3). Histopathology revealed pseudocarcinomatous hyperplasia and occasional multinucleated giant cells. Growth of Sporothrix schenckii was depicted in tissue culture. Because of the patient's diabetes and renal failure, terbinafine therapy was chosen over itraconazole, which has known drug interactions with antidiabetic agents. Complete response was achieved with 125 mg PO daily (renal dose adjustment) for 2 months.

Figure 1.

Tumor in the frontal region with 4 cm diameter, punctuated in its center with keratosic material.

Figure 2.

Tumor in the frontal region with 4 cm diameter, punctuated in its center with keratosic material.

Figure 3.

Partially regression of the lesion after incisional biopsy.

Sporotrichosis is a subcutaneous or systemic infection caused by the dimorphic fungus S. schenckii. Starting as an outbreak in 1998, several cat-transmitted cases have been regularly reported in Rio de Janeiro, Brazil.1 Presentation varies according to virulence of the strain and host immune status. Main forms are lymphocutaneous and fixed cutaneous, with the latter occasionally resembling rosacea, pyoderma gangrenosum, and keratoacanthomas.2

Despite the striking resemblance of the clinical behavior with keratoacanthoma, histopathology and culture confirmed sporotrichosis in this case.