A 63-year-old female with a 25-year history of an exquisitely painful callus located at the lateral margin of the right fifth metatarsal is seen by you in your office. The patient states that she must have the lesion debrided every two months to avoid pain when wearing shoes. She warns you in advance to be careful when you debride the lesion because the lesion also hurts when it is debrided. After you remove the overlying callus, you notice a mosaic-looking lesion with multiple small keratotic plugs seated next to each other, forming a plaque (Figs. 1A and 1B). No pinpoint bleeding is noted. You decide to bluntly remove the lesion, thinking it is not a simple callus. Histologically, multiple rectangular-shaped plugs of keratin are seen with rounded bases. Beneath these keratinous plugs, the underlying epithelium is hyperplastic. Each plug is separated by air...

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