What is the recommended treatment for borderline phyllodes tumors?

Treatment of Borderline Phyllodes Tumors

Borderline phyllodes tumors should be treated with wide excision achieving negative surgical margins, with adjuvant radiotherapy reserved only for high-risk cases where clear margins cannot be achieved surgically. 1

Primary Surgical Management

Wide excision with clear margins is the definitive treatment for borderline phyllodes tumors. 1

• Target surgical margins of ≥1 cm to minimize local recurrence risk 1
• Either breast-conserving surgery or mastectomy can be performed, depending on tumor size and location 1
• No axillary staging or lymph node dissection is required, as phyllodes tumors rarely metastasize to lymph nodes 1
• Mastectomy is indicated only when adequate margins cannot be achieved with breast conservation 1

Margin Status and Re-excision

The most critical factor determining local recurrence is achieving negative margins 1:

• If margins are positive or <1 mm, repeat surgical excision should be performed to achieve clear margins 1
• Margins <1 cm are associated with heightened local recurrence risk but are not an absolute indication for mastectomy 1
• Recent evidence suggests that borderline tumors with margins ≤1 mm have increased recurrence risk 2

Role of Adjuvant Radiotherapy

In borderline phyllodes tumors, surgical excision alone is likely to be curative if negative margins are achieved. 1

Adjuvant radiotherapy should be considered only in high-risk cases of borderline phyllodes, specifically: 1

• Large tumors (>5 cm)
• Infiltrative margins
• Cases where clear margins could not be achieved surgically despite re-excision attempts

Evidence for Radiotherapy

• Adjuvant radiotherapy improves local control but not survival in breast sarcomas 1
• Meta-analysis data shows radiotherapy reduces local recurrence rates after breast-conserving surgery (HR=0.31) but not after mastectomy 3
• The UK guidelines (2025) specifically state radiotherapy is for improving local control when surgical margins are inadequate 1

Reconstruction Considerations

Immediate reconstruction should be avoided in borderline phyllodes tumors with high-risk features. 1

• Delayed reconstruction is preferred when primary oncological management is completed and local recurrence risk has diminished 1
• This approach is particularly important for large tumors that may require postoperative radiotherapy 1

Follow-up for Recurrence

Local recurrence occurs in approximately 7-24% of borderline phyllodes tumors, with most recurrences in patients who had positive or close margins initially 4, 5, 2

For locally recurrent disease: 1

• Re-excision with wide margins without axillary staging
• Consider postoperative radiation therapy, especially if additional recurrence would create significant morbidity 1

Key Clinical Pitfalls

Common diagnostic challenge: Core needle biopsy may not reliably distinguish borderline phyllodes from benign fibroadenoma preoperatively 1

Avoid these errors:

• Do not perform axillary staging—it is unnecessary and adds morbidity 1
• Do not use adjuvant chemotherapy or endocrine therapy—these have no proven role in borderline phyllodes 1
• Do not routinely recommend radiotherapy for all borderline tumors—reserve it for high-risk cases only 1

Multidisciplinary Management

Borderline phyllodes tumors should be referred to specialist sarcoma centers for pathology review and multidisciplinary team discussion. 1

• Close collaboration between breast cancer and sarcoma multidisciplinary teams is necessary 1
• This ensures appropriate risk stratification and treatment planning 1