Plantar fibroma and plantar fibromatosis are two common causes of lumps in the foot's arch, according to the American Orthopaedic Foot & Ankle Society. A benign nodule, plantar fibroma typically develops on people between the ages of 20 and 60 years old. The fibroma grows slowly to a size of less than an inch. Plantar fibromatosis is a multiplanar fibroma that is more invasive and grows more rapidly than plantar fibromas, although both are benign.
Ganglion cysts may also cause lumps in the arches of the feet, explains Mayo Clinic. Filled with fluid, ganglion cysts are oval or round in shape, with sizes ranging from small and pea-shaped to an inch in diameter. Ganglion cysts cause pain when they press against nerves. The cyst may not require treatment, although if it causes pain, a doctor may use a needle to drain it.
Plantar warts can also cause lumps on the foot's arch, advises WebMD. Spread by direct or indirect contact with the human papillomavirus, plantar warts are harmless but may cause pain or irritation. Calluses and corns are sometimes mistaken for plantar warts. When grown in clusters, plantar warts are called mosaic warts. Home remedies to treat plantar warts can take weeks to months and include the use of duct tape or over-the-counter medications. A doctor can also remove the wart by freezing it with liquid nitrogen, via laser surgery or using topical or injectable medications.