A 77-year-old woman presented with a 5-year history of a slowly growing lesion on the upper part of her right arm. The lesion had become painful and was regularly irritated by catching on her clothes. Physical examination revealed a brightly erythematous 8 × 12-mm irregular nodule with a small ulceration on the medial aspect of the upper part of her right arm (Figure 1). The results of the rest of the skin examination were unremarkable. An excisional biopsy was performed (Figure 2 and Figure 3).