A plantar fibroma is a benign (non-cancerous) nodule that typically grows in the arch of the foot and usually appears between ages 20 and 60. It usually is slow-growing and often less than one inch in size. Some can grow faster and are considered plantar fibromatosis.
A plantar fibroma or fibromatosis is a disease of the fibrous tissue that grows deep in the skin and along the plantar fascia.
The main symptom is a mass on the bottom of the foot, roughly in the middle of the arch or instep, between the heel pad and the forefoot (front of the foot) fat pad. The mass will cause a soft curve in the contour of the bottom of the foot that may be painful with pressure or shoe wear.
The cause is unknown but thought to have a genetic component. Plantar fibromas are more prominent in people with northern European genetic backgrounds. Trauma to the foot does not seem to be a factor. Alcohol consumption may be a factor.
Plantar fibromas reside in the plantar fascia of the foot between the skin and the first 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.
Your foot and ankle orthopaedic surgeon will conduct a physical exam. If a plantar fibroma exists, they will find a mass in the plantar fascia in the arch. The mass has no swelling, increased warmth, or redness. It is firm and does not move. There are no skin changes. Advanced imaging is usually not needed but MRI will show the fibroma in the plantar fascia layer.
There are a few conditions that can cause soft-tissue masses in the foot, including cysts, swollen tendons or tendon ruptures, nerve tumors (neurilemomas), or fat tumors. Foreign body reactions from previous penetrating trauma also can cause a mass in the bottom of the foot, as can an infection. A more serious synovial cell sarcoma, a malignancy, usually will show calcification on X-ray and a more worrisome appearance on MRI. Clinical exam, X-ray, and sometimes an MRI may be needed for diagnosis. Biopsy usually is not needed.
Generally, a plantar fibroma is treated without surgery. If you are considering surgery, your surgeon will likely look at the other foot and both hands. If you exhibit fibromatosis on the palms of your hands (Dupuytren's) or the other foot, recurrence is likely. Most patients can be treated conservatively through orthotics (inserts) and stretching. Surgery is considered only after all non-surgical options have been exhausted.
Recovering from excision (surgical removal) of the plantar fibroma will take time. Typically, a non-weightbearing splint is placed the time of surgery. After skin sutures are removed in 10-14 days, a CAM boot or a short leg cast is placed to protect the plantar fascia for several weeks. You will likely need to keep weight off your foot for at least 6 weeks while the surgery heals. If the surgery is more complex with excision of the lesion, plantar fascia, and overlying skin with skin grafting, it may take months to recover.
Potential complications include wound drainage or infection, a healed but painful wound, and chronic neuritic pain, especially for an invasive lesion or in revision surgery. There is a high recurrence rate of the mass returning after surgical removal of the plantar fibroma.
At least 1-2 weeks, if you can keep your foot elevated and stay on crutches, or longer if this is not possible. It will take at least 6 weeks for the excised portion of the plantar fibroma to heal in a cast or CAM boot.
There is no harm in waiting. This is a benign (non-cancerous) condition which typically is treated without surgery.
Contributors/Reviewers: Naomi Shields, MD; Wen Chao, MD
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