What are the recommended margins for surgical excision of phyllodes tumors?

Surgical Margins for Phyllodes Tumors

All phyllodes tumors—benign, borderline, and malignant—require surgical excision with tumor-free margins of ≥1 cm. 1, 2

Primary Surgical Approach

• Lumpectomy or partial mastectomy is the preferred surgical therapy for all phyllodes tumor subtypes. 1
• Total mastectomy should be performed ONLY when negative margins cannot be achieved with breast-conserving surgery. 1, 2
• Axillary staging or lymph node dissection is NOT necessary because phyllodes tumors rarely metastasize to axillary lymph nodes. 1, 2

The Margin Controversy: Guidelines vs. Contemporary Evidence

While current NCCN guidelines recommend ≥1 cm margins for all phyllodes tumors 1, 2, recent multi-institutional data challenges this one-size-fits-all approach:

For Benign Phyllodes Tumors:

• A negative margin (tumor not at ink) may be sufficient for benign phyllodes, and progressively wider margins do not reduce local recurrence risk. 3, 4
• A 2021 multi-institutional study of 550 cases found that wider margin width (≥2 mm vs <2 mm) was NOT associated with reduced local recurrence for the entire cohort. 3
• European data confirms no difference in recurrence rates between 1 mm and 10 mm margins for benign tumors (5.7% vs 7.9%, p=0.124). 4
• Re-excision of a negative margin for benign phyllodes is NOT recommended, regardless of margin width. 3

For Borderline and Malignant Phyllodes Tumors:

• Maintain the ≥1 cm margin recommendation for borderline and malignant subtypes. 1, 2
• Borderline and malignant tumors with positive or ≤1 mm margins have significantly increased recurrence risk. 5
• In one series, 10 of 11 locally recurrent tumors had positive or ≤1 mm margins at initial surgery. 5
• Stromal overgrowth combined with positive margins is particularly high-risk and warrants re-excision. 6

Critical Clinical Algorithm

At Initial Surgery:

1. If preoperative diagnosis suggests phyllodes (rapidly enlarging mass >2 cm), plan for ≥1 cm margins. 1
2. If diagnosed as phyllodes only on final pathology, assess margin status and tumor grade. 1

Post-Operative Margin Management:

For Benign Phyllodes:

• Negative margin (any width): No re-excision needed 3, 4
• Positive margin (tumor at ink): Consider re-excision, but recurrence risk remains low even without it (2.7% in one series) 3

For Borderline/Malignant Phyllodes:

• Margin <1 mm or positive: Re-excision strongly recommended 1, 2, 5
• Margin ≥1 cm: No further surgery needed 1, 2
• If clear margins cannot be achieved despite re-excision attempts, consider adjuvant radiotherapy 2

Key Pitfalls to Avoid

• Do NOT routinely re-excise benign phyllodes tumors with narrow but negative margins—this adds morbidity without proven benefit. 3, 4
• Do NOT accept positive margins in borderline/malignant tumors without attempting re-excision. 5, 6
• Do NOT perform mastectomy solely to achieve wider margins if breast conservation with adequate margins is feasible. 1
• Do NOT use core needle biopsy results alone to plan surgery—these often underestimate phyllodes tumors or miss them entirely. 1, 2

When Margins Cannot Be Achieved

• If ≥1 cm margins cannot be obtained with breast-conserving surgery, proceed to mastectomy. 1, 2
• For borderline/malignant tumors >5 cm, infiltrative margins, or cases where clear margins remain unachievable, consider adjuvant radiotherapy. 2
• Radiotherapy improves local control but not survival. 2

Recurrence Management

• Re-excision with wide margins (≥1 cm) without axillary staging is the treatment for local recurrence. 7
• Consider postoperative radiation therapy if additional recurrence would create significant morbidity (e.g., chest wall recurrence after salvage mastectomy). 7
• Borderline and malignant recurrent tumors should be referred to specialist sarcoma centers for multidisciplinary review. 7