A plantar fibroma is a benign nodule that grows on the bottom of the foot that usually appears in the second through sixth decade of life. It is usually slow growing and measures less than an inch in size. More invasive, rapidly growing (aggressive), and multiplanar fibromas are considered plantar fibromatosis. Both of them are benign tumors made up of fibrocytes, or cells, found in ligaments.
Symptoms and Clinical Presentation
Symptoms consist of a painful mass on the bottom of the foot roughly between the heel pad and the forefoot pad (in the middle of the arch or instep). The mass will cause a soft convexity in the contour of the bottom of the foot that may be painful with pressure or in shoewear.
Cause (including risk factors)
The cause is unknown but is thought to have a genetic component. Trauma to the foot does not seem to be a factor.
Plantar fibromas reside in the deep fascia of the foot between the skin and the first (superficial) layers of muscle. The more aggressive condition of plantar fibromatosis may involve the skin and the muscle layers and may also wrap around the local digital nerves and arteries.
There are a few conditions that can cause soft tissue masses in the foot, including cysts, swollen tendons, tendon ruptures, nerve tumors (neurilemomas), or fat tumors. Foreign body reactions from previous penetrating trauma can also cause a mass in the bottom of the foot, as can an infection. A more serious synovial cell sarcoma, a malignancy, will usually show calcification on X-ray and a more worrisome appearance on MRI clinical exam. Biopsy is usually not needed.
Frequently Asked Questions
How did I get it?
Plantar fibroma and plantar fibromatosis are inherited.
*Source: American Orthopaedic Foot & Ankle Society® http://www.aofas.org