Histopathologic examination showed epidermal acanthosis and nests of large, predominantly spindle cell–shaped melanocytes at the dermoepidermal junction and in the dermis (Figure 2). Some of the cells demonstrated mitotic activity. Atypical mitoses were not seen. Melanin pigment was absent.
The tumor nests were negative for anticytokeratin antibodies AE1 and AE3. They were also positive for S100 (Figure 3) and negative for HMB 45.
Dome-Shaped Partly Umbilicated Tumor on the Ear. Arch Dermatol. 1998;134(12):1627-1632. doi: