Plantar Fibromatosis

Description

Plantar fibromatosis, also known as Ledderhose disease, is a benign fibroproliferative condition involving the plantar aponeurosis of the foot. It is part of the spectrum of superficial fibromatoses, which also includes palmar fibromatosis (Dupuytren contracture). The condition is characterised by the development of nodular or plaque-like fibrous proliferations within the superficial plantar fascia, typically medial to the central band. These lesions may be asymptomatic or may cause pain due to pressure on the overlying skin, nerves, or when interfering with footwear.

It tends to affect middle-aged individuals and may be unilateral or bilateral. Although benign, plantar fibromatosis is locally infiltrative and may recur after resection.

Pathogenesis

The pathological process involves proliferation of fibroblasts and myofibroblasts within the plantar fascia, which deposit excessive collagen, primarily type I and III. The process is thought to be reactive rather than neoplastic, triggered by repetitive trauma, microvascular injury, or genetic predisposition.

Histologically, the disease progresses through three stages:

1. Proliferative phase: Hypercellular, with abundant myofibroblasts and minimal collagen.
2. Active phase: Increased collagen production, moderate fibroblast activity.
3. Mature phase: Dense collagen bundles with reduced cellularity and vascularity.

The nodules arise most commonly within the medial aspect of the plantar fascia and may coalesce over time. Unlike desmoid fibromatosis, the process remains superficial and does not invade deep fascial planes or musculature.

Subtypes

There are no formal histological subtypes of plantar fibromatosis. However, based on behaviour and extent, lesions may be described as:

• Solitary nodular – most common and often asymptomatic.
• Diffuse or confluent plaques – larger, may cause mechanical symptoms.

Epidemiology, Risk Factors & Associations

Epidemiology

• Middle-aged adults; peak incidence between 40–60 years.
• Male predilection.

Risk Factors

• Repetitive mechanical trauma.
• Diabetes mellitus.
• Alcoholism.
• Epilepsy (particularly with chronic phenytoin use).
• Family history of fibromatoses.

Associations

• Dupuytren contracture (palmar fibromatosis).
• Peyronie disease (penile fibromatosis).
• Keloids and hypertrophic scars.

These associations suggest a shared fibromatosis diathesis.

Clinical Features

• Firm, palpable subcutaneous nodules on the medial aspect of the foot arch.
• Usually painless, but may become tender with ambulation or tight footwear.
• Bilateral in approximately 25% of cases.
• Fixed to the underlying plantar fascia but not the overlying skin.
• Skin ulceration and neurovascular involvement are rare.

Complications

• Local pain and discomfort with walking.
• Restriction of footwear choices due to mass effect.
• High recurrence rate post-surgical excision.
• No malignant transformation.

Pathological Features

Histopathology

Macroscopic

• Firm, grey-white nodules within the medial plantar fascia.
• May be solitary or multiple; often poorly circumscribed.

Microscopic

• Proliferation of bland spindle-shaped fibroblasts and myofibroblasts.
• Storiform or fascicular growth pattern.
• Dense collagen deposition in mature lesions.
• Mitotic activity is low; no cytologic atypia.
• Entrapment of adjacent structures such as tendons or nerves is not typical.

Serology

• Not contributory; no tumour markers or serologic tests are specific.

Biochemistry

• Normal inflammatory and metabolic panels unless associated systemic disease is present.

Immunohistochemistry

• Positive for smooth muscle actin (SMA) and vimentin.
• Negative for S100 and desmin, excluding neural or muscular origin.

Molecular

• No consistent genetic abnormalities.
• Unlike desmoid fibromatosis, does not typically show beta-catenin nuclear positivity.

Radiological Features

General Features

• Imaging is not always required but aids in defining extent and planning management.
• First-line modality: MR.
• Lesions are located along the medial aspect of the plantar aponeurosis, often subcutaneous.

XR

• Often normal.
• May show subtle soft tissue prominence along the medial foot arch.

CT

• Demonstrates soft tissue nodules in the plantar fascia, isodense to muscle.
• Can show fibrous plaque extent and calcification, if present.

MR

• Typically located superficial to the flexor digitorum brevis and deep to the subcutaneous fat.
• T1: Isointense to muscle.
• T2: Variable; early lesions may be mildly hyperintense, while mature fibrous tissue appears hypointense.
• STIR: May show slightly increased signal if oedematous.
• Post-contrast T1 Gad+: Enhances variably; lesions with higher cellularity or vascularity enhance more.

US

• Well-suited for superficial nodule detection.
• Hypoechoic nodules embedded in the plantar fascia.
• Non-compressible, with variable vascularity on Doppler.

NM

• Not indicated.

Grading and Staging

No formal grading or staging system exists. Lesions may be classified descriptively as nodular or plaque-like and evaluated based on extent and symptomatology.

Diagnosis

• Clinical diagnosis with confirmatory imaging in uncertain or symptomatic cases.
• Biopsy is rarely needed unless atypical features (e.g. rapid growth, pain, deep extension).

Differential Diagnosis

Image-based

• Desmoid fibromatosis: Deeper, more infiltrative; often in muscular planes.
• Soft tissue sarcoma: Rapid growth, heterogeneous signal, necrosis or calcification. Typically T1 low, T2 high and heterogenous enhancement.
• Lipoma: Homogeneously hyperintense on T1, suppresses on fat-saturation sequences.
• Neurogenic tumours: Associated with neural pathways, often positive for S100.

Clinically-based

• Plantar fascia rupture or strain: Acute onset, typically post-trauma.
• Ganglion cyst: More fluctuant and transilluminant.
• Morton neuroma: Localised between metatarsal heads, not along fascia.

Management

Conservative

• First-line: Footwear modification with soft inserts or offloading orthotics.
• Intralesional corticosteroid injections for symptomatic lesions.
• Physical therapy and stretching exercises.

Surgical

• Reserved for persistent, painful, or functionally limiting lesions.
• Local excision is associated with high recurrence (up to 50%).
• Wide excision or fasciectomy may reduce recurrence but risks plantar nerve injury and wound complications.

Emerging Therapies

• Radiation therapy: Inhibits fibroblast proliferation; limited use due to long-term risks.
• Collagenase injections: Under investigation; used in Dupuytren disease.
• Antifibrotic agents: Still experimental.