Is a negative margin necessary for excision of Phyllodes (Phyllodes tumor) tumors?

Negative Margins for Phyllodes Tumor Excision

For phyllodes tumors, negative margins are necessary during excision, with a recommended margin width of ≥1 cm for all grades, though recent evidence suggests narrower negative margins may be sufficient for benign phyllodes tumors. 1

Margin Recommendations by Tumor Grade

Benign Phyllodes Tumors

• Negative margins are recommended, but the traditional ≥1 cm margin may not be necessary 1, 2
• Recent evidence from a large multi-institutional study (550 cases) suggests that for benign phyllodes tumors:
  • Re-excision is not recommended if margins are negative, regardless of width 2
  • Conservative management may be appropriate even with close margins 3

Borderline and Malignant Phyllodes Tumors

• Wide local excision with ≥1 cm margins remains the standard recommendation 1
• Tumors with positive or narrow (<1 mm) margins have significantly increased risk of recurrence 4
• Re-excision is strongly recommended if margins are positive or narrow (<1 cm) 1

Risk Factors for Local Recurrence

Local recurrence risk correlates with:

• Margin status (positive margins increase risk) 5
• Tumor grade (borderline and malignant have higher recurrence rates) 1
• Mitotic rate (≥10 mitoses/10 HPF significantly increases risk) 6
• Tumor size (particularly tumors ≤5 cm with high mitotic rates) 6

Surgical Approach Algorithm

1. Initial Excision:

   • Aim for ≥1 cm margins for all phyllodes tumors 1
   • Consider the cosmetic outcome and breast conservation when possible

2. If Margins are Positive:

   • For benign phyllodes: Consider observation with close follow-up, as recurrence rates remain low (2.7%) even without re-excision 2
   • For borderline/malignant phyllodes: Re-excision is strongly recommended 1, 4

3. If Margins are Negative but <1 cm:

   • For benign phyllodes: Observation is reasonable as wider margins don't significantly reduce recurrence 2, 3
   • For borderline/malignant phyllodes: Consider re-excision, especially if margins are <2 mm 1, 4

4. If Re-excision Not Feasible:

   • Consider adjuvant radiation therapy, especially for borderline/malignant tumors with close margins 1

Important Caveats

• The traditional teaching of ≥1 cm margins is being challenged by newer evidence, particularly for benign phyllodes tumors 2, 4, 3
• Small tumors (≤5 cm) with high mitotic rates (≥10/10 HPF) have the highest recurrence risk (55.6%) and require particular attention to margin status 6
• Mastectomy should be reserved for cases where negative margins cannot be achieved with breast conservation 1
• Lymph node involvement is rare; axillary staging is not recommended 1

Follow-up Recommendations

• Regular surveillance is essential, as most recurrences occur within the first few years 1
• For benign phyllodes with close margins, imaging can be performed based on clinical symptoms 4
• Recurrent disease should be managed with re-excision with wide margins 1