A 19-year-old man presented with a 2- to 3-week history of a pink, slightly painful tumor on the helix of the left ear. Physical examination revealed a solitary, dome-shaped, reddish pink, 7-mm-diameter lesion that was slightly umbilicated and crusted (Figure 1). The preliminary diagnosis was keratoacanthoma. Excisional biopsy of the tumor was performed. The histologic findings are shown in
Figure 2. Staining with antibodies to S100 protein is shown in Figure 3.
Filo V, Galbavy S, Pec J. Dome-Shaped Partly Umbilicated Tumor on the Ear. Arch Dermatol. 1998;134(12):1627-1632. doi: