A plantar fibroma is a fibrous knot (nodule) in the arch of the foot. It is embedded within the plantar fascia, a band of tissue that extends from the heel to the toes on the bottom of the foot. A plantar fibroma can develop in one or both feet, is benign (non-malignant). The characteristic sign of a plantar fibroma is a noticeable lump in the arch that feels firm to the touch. This mass can remain the same size or get larger over time, or additional fibromas may develop. People who have a plantar fibroma may or may not have pain. Non-surgical treatment may help relieve the pain of a plantar fibroma, although it will not make the mass disappear.