The corns are usually as large as beans or larger, with clear boundaries, yellowish or dark yellow. Callus is a waxy yellow, flat or slightly elevated limited keratinous hypertrophic plaque, hard and slightly transparent, border is not clear, the center is thicker, the edge is thinner.

The foot skin localized long-term pressure and friction caused by limited, cone-shaped keratosis. It is commonly known as a "thorn". People who stand and walk for a long time are more likely to occur, friction and pressure is the main cause. Tight boots or deformed foot bones can cause the corns of the foot to thicken at the site of friction or pressure, and advance inward to become conical corns with inward facing tips.

The lesion is a round or oval limited keratosis, the size of a pinhead to a broad bean, yellowish or dark yellow, the surface is smooth and flat or slightly elevated, the boundary is clear, and there is an inverted conical keratin plug embedded in the dermis in the center. Because the tip of the keratin plug stimulates the nerve endings in the papilla of the dermis, it causes pain when standing or walking.