A 75-year-old female presented with a solitary nodule, 3 mm in diameter, on the dorsum of her nose that she had had for 20 years. It had a central pore-like opening plugged with keratin. A dermoscopic examination demonstrated several small keratotic areas that looked like columns or small blocks in the central pore, and a few tips extended from the edges to the center. The lesion was completely excised. A pathological examination revealed a central epidermal cavity filled with keratinous material from which emerged a few horn-shaped projections. Multiple tumor lobules extended from the wall of the cavity into the dermis. These lobules were composed mainly of squamous cells and partly of clear cells showing differentiation of the outer root sheath. We made a diagnosis of pilar sheath acanthoma (PSA) based on these findings. PSA has been reported in only 8 cases in Japan, and we are not aware of previous descriptions in the literature of the dermoscopic features of PSA. Although careful observation using loupes can show the same pattern, we think the dermoscopic pattern in our case is characteristic of PSA, and we suggest calling it “central multiple horn pattern”.
