What is the recommended management for a borderline phyllodes tumor of the breast?

Management of Borderline Phyllodes Tumors

Perform wide excision with surgical margins ≥1 cm as the definitive treatment for borderline phyllodes tumors, without axillary staging. 1, 2, 3

Primary Surgical Approach

Wide excision with clear margins is the cornerstone of management:

• Target surgical margins of at least 1 cm to minimize local recurrence risk 1, 2, 3
• Breast-conserving surgery (lumpectomy or partial mastectomy) is the preferred approach when adequate margins can be achieved 1, 2, 3
• Mastectomy is indicated only when negative margins cannot be obtained with breast conservation 1, 2, 3
• Never perform axillary staging or lymph node dissection—phyllodes tumors rarely metastasize to lymph nodes, and this adds unnecessary morbidity 1, 2, 3

Critical Margin Considerations

The margin status is more important than histologic subtype for predicting local recurrence 3. While the 1 cm margin target is standard 1, 2, 3, the evidence shows some nuance:

• Margins <1 mm are inadequate and associated with higher recurrence rates 1, 4
• Local recurrence correlates directly with positive margins or margins <1 cm 5, 4
• However, some data suggest that close margins (<10 mm) in benign and borderline tumors may not require systematic re-excision if the tumor appears well-circumscribed 6
• Caution: A recent case report documented a satellite nodule found at re-excision of a well-circumscribed borderline tumor, supporting the continued recommendation for wide margins 7

Practical algorithm for margin management:

• If initial excision achieves ≥1 cm margins: no further surgery needed 1, 2, 3
• If margins are <1 cm but the tumor is well-circumscribed on pathology: consider re-excision versus close surveillance based on individual risk factors 6
• If margins are positive (tumor at ink): re-excision is mandatory 1, 4

Adjuvant Radiotherapy Decision-Making

Do not routinely recommend radiotherapy for all borderline phyllodes tumors—reserve it only for high-risk cases 2, 3:

Specific indications for adjuvant radiotherapy:

• Large tumors >5 cm 2, 3, 8
• Infiltrative margins on pathology 2, 8
• Cases where clear margins could not be achieved surgically despite re-excision attempts 2, 8
• Local recurrence, especially if additional recurrence would create significant morbidity (e.g., chest wall recurrence after salvage mastectomy) 1, 2, 8

Evidence supporting selective use:

• Radiotherapy improves local control (from 34-42% to 90-100% at 5 years) but does not improve overall survival 2
• The benefit is primarily in preventing local recurrence in high-risk scenarios 2, 8

Technical radiotherapy details when indicated:

• Target the whole breast (after breast-conserving surgery) or chest wall (after mastectomy) to 50-60 Gy 2
• Do not include axillary, supraclavicular, or internal mammary lymph nodes—phyllodes tumors are sarcomas, not epithelial breast cancers 2

Reconstruction Timing

Avoid immediate reconstruction in borderline phyllodes with high-risk features (large size, infiltrative margins, close margins) 2, 3:

• Delayed reconstruction is preferred after primary oncological management is completed 2, 3
• Wait until local recurrence risk has diminished, typically 2 years 2

Management of Local Recurrence

If local recurrence develops after initial treatment 1, 8:

Diagnostic workup:

• History and physical examination focusing on the previous surgical site 8
• Ultrasound as primary imaging, plus mammogram of entire breast 1, 8
• Tissue sampling with histology preferred over core biopsy 1, 8
• Chest imaging to exclude metastatic disease 1, 8

Treatment approach:

• Re-excision with wide margins (≥1 cm) without axillary staging 1, 8
• Consider postoperative radiation therapy if additional recurrence would create significant morbidity 1, 2, 8

What NOT to Do: Common Pitfalls

Avoid these management errors:

• Do not rely on core needle biopsy or FNA to definitively exclude phyllodes tumor preoperatively—these may not distinguish borderline phyllodes from benign fibroadenoma 1, 2, 3, 8
• Do not perform routine axillary staging—this is unnecessary and adds morbidity without benefit 1, 2, 3
• Do not use adjuvant chemotherapy or endocrine therapy—these have no proven efficacy in borderline phyllodes tumors 2, 3
• Do not routinely recommend radiotherapy for all borderline tumors—reserve for high-risk cases only 2, 3
• Do not accept inadequate surgical margins—this is the most important modifiable factor for preventing local recurrence 3, 4

Surveillance Strategy

Follow-up schedule after definitive treatment:

• Every 3-4 months during the first 2 years (when most recurrences occur) 2, 6
• Every 6 months for years 3-5 2
• Annually thereafter for lifelong follow-up 2

Surveillance components:

• Clinical examination of the surgical site and chest wall at each visit 2
• Annual mammography of the contralateral breast 2
• Annual chest imaging (plain radiograph or low-dose CT) to detect pulmonary metastases, the most common distant site 2
• Targeted ultrasound or MRI only if palpable abnormality detected 2

Multidisciplinary Management

Refer borderline phyllodes tumors to specialist sarcoma centers for:

• Pathology review to confirm diagnosis and grade 2, 3, 8
• Multidisciplinary team discussion involving both breast cancer and sarcoma specialists 2, 3, 8
• Appropriate risk stratification and treatment planning 2, 3, 8