Differential Diagnosis of Non-Painful Plantar Foot Nodules
The primary differential diagnoses for non-painful nodules on the plantar aspect of the foot include plantar fibromatosis (Ledderhose's disease), lipomas, benign plantar nodules of childhood (piezogenic papules), and less commonly Morton's neuroma or giant cell tumor of tendon sheath.
Most Common Etiologies
Plantar Fibromatosis (Ledderhose's Disease)
- Presents as firm nodules along the medial band of the plantar fascia, typically in the central medial portion 1, 2
- Characterized by gradual-growing nodules with possible sclerosis and shrinkage of the entire fascia 2
- Histologically linked to Dupuytren's contracture and Peyronie's disease, representing a proliferative disorder of collagen and fibroblasts 2
- Associated risk factors include diabetes mellitus, trauma, anticonvulsant use, frozen shoulder, alcohol consumption, and liver disease 2
- MRI demonstrates nodules along the plantar fascia with characteristic signal intensity patterns 1
- Ultrasound typically confirms the diagnosis, showing tissue accumulation distinct from normal fascia 2
Lipomas
- Exceptionally rare at the plantar level but must be considered in the differential 3
- Present as slow-growing, asymptomatic soft tissue masses 3
- MRI is the technique of choice for diagnosis, showing characteristic fatty signal intensity 4, 3
- Surgical excision provides definitive histological diagnosis and restores normal plantar support 3
Benign Plantar Nodules of Childhood (Piezogenic Papules)
- Localized, bilateral, painless, symmetric papuloid lesions in the posteromedial part of the heel 5
- Probably congenital and represent a normal anatomic variant 5
- Mean presentation age approximately 45 months, with most cases being bilateral (83% in one series) 5
- Sonography shows accumulation of tissue similar to subcutaneous fat, sufficient for diagnosis without biopsy 5
- Persist throughout childhood but remain asymptomatic with normal functional outcomes 5
- No treatment required; surgical excision is unnecessary 5
Diagnostic Approach
Initial Imaging
- Location and signal characteristics on MRI can differentiate between Morton's neuroma, giant cell tumor of tendon sheath, and plantar fibromatosis 4
- Ultrasound can confirm cystic versus solid nature of lesions, distinguishing ganglia, synovial cysts, and bursitis from solid masses 4
- For plantar fibromatosis specifically, ultrasound is typically sufficient, with MRI reserved for more aggressive or advanced presentations 2
Key Imaging Features
- Cystic lesions (ganglia, synovial cysts, bursitis) can be confirmed with MRI or sonography 4
- Noncystic lesions require assessment of location, signal characteristics, presence of mineralization, and enhancement patterns 4
- Patient age aids in narrowing differential diagnosis based on incidence patterns of specific neoplasms 4
Clinical Pitfalls
Common Diagnostic Errors
- Delayed diagnosis is common due to slow, asymptomatic evolution of plantar soft tissue tumors 3
- Do not perform unnecessary biopsies for benign plantar nodules of childhood—sonography showing fatty tissue is diagnostic 5
- Plantar fibromatosis has high recurrence rates even after surgical excision, so conservative management should be attempted first 2
Management Considerations
- For plantar fibromatosis, multiple conservative options exist including steroid injections, verapamil, radiation therapy, extracorporeal shock wave therapy, and collagenase 2
- Surgical intervention for plantar fibromatosis should be reserved for failed conservative treatment, with expectation of recurrence 2
- Lipomas require surgical excision for definitive diagnosis and symptom resolution 3
- Benign plantar nodules of childhood require only reassurance and observation 5