Nov 13, - Plantar fibroma. Plantar fibroma is a hereditary condition that causes a nodule to form on the bottom of the foot. The nodule forms in the middle (beneath the arch) of your foot. It may be painful when pressure is applied. Apr 6, - Learn to spot bunions, corns, athlete's foot, plantar warts, and other common foot problems in this WebMD slideshow -- and learn what.