Treatment of Mast Cell Tumors on the Foot
Wide surgical excision with tumor-free margins of at least 1 cm is the primary treatment for mast cell tumors on the foot, with adjuvant radiation therapy recommended for high-grade tumors or when clean margins cannot be achieved. 1
Diagnostic Approach
- Obtain a fine needle aspirate or biopsy to confirm diagnosis
- Histopathologic grading is essential for treatment planning and prognosis
- Staging should include:
- Physical examination with careful assessment of regional lymph nodes
- Chest radiographs to exclude lung metastases
- Advanced imaging (CT scan) for accurate surgical planning of foot tumors
Surgical Management
- Wide surgical excision is the cornerstone of treatment 1
Surgical Considerations for Foot Location
- Foot location presents unique challenges:
- Limited tissue availability for reconstruction
- Higher risk of wound healing complications (20% complication rate) 3
- May require partial amputation or limb amputation for adequate margins
Adjuvant Therapy Options
Radiation Therapy
- Indicated when:
- Clean surgical margins cannot be achieved
- Incomplete excision of high-grade tumors
- Tumors with deep tissue invasion
Systemic Therapy
Toceranib (Palladia):
- FDA-approved for mast cell tumors
- Demonstrated 37.2% objective response rate in clinical trials 4
- Dosage: 3.25 mg/kg orally every other day
- Consider for unresectable tumors or as adjuvant therapy for high-grade tumors
Prednisone:
- Can be used for tumor cytoreduction or palliation
- 20% response rate at 1 mg/kg daily 5
- May be combined with other therapies
Post-Treatment Monitoring
- Regular follow-up examinations every 3 months for the first 2-3 years 1
- Monitor surgical site for local recurrence
- Assess regional lymph nodes for potential metastasis
- Consider chest radiographs every 3-4 months for high-grade tumors 1
Prognostic Factors
- Complete surgical excision with clean margins is the most important prognostic factor
- No local recurrence or metastatic disease has been reported following excision with lateral margins ≥10 mm and deep margins ≥4 mm 6
- Tumor grade significantly impacts prognosis and treatment decisions
- Foot location may be associated with more aggressive behavior and higher risk of complications
Treatment Algorithm
- Confirm diagnosis and grade with histopathology
- Perform complete staging
- For resectable tumors:
- Proceed with wide surgical excision (≥1 cm margins)
- If complete excision achieved: monitor
- If incomplete excision: consider re-excision or radiation therapy
- For unresectable tumors:
- Consider radiation therapy
- Consider systemic therapy with toceranib
- Palliative care with prednisone if other options not feasible
Caution
- Avoid narrow surgical margins as they significantly increase recurrence risk
- Do not delay definitive treatment as mast cell tumors can progress rapidly
- Recognize that foot location presents unique surgical challenges and may require more aggressive approaches