What is the treatment for metaplastic carcinoma of the breast?

Treatment of Metaplastic Carcinoma of the Breast

Metaplastic breast carcinoma should be treated as an epithelial breast cancer (not as a sarcoma), following standard breast cancer treatment protocols based on hormone receptor and HER2 status, despite its sarcomatous histologic features. 1

Critical Classification Point

• Metaplastic breast carcinomas (also called carcinosarcomas) are epithelial neoplasms that must be managed according to their epithelial nature, not as sarcomas. 1
• This distinction is crucial because referring these patients to sarcoma protocols leads to suboptimal treatment outcomes. 1
• The sarcomatous differentiation within these tumors is a histologic feature, but the tumor biology and treatment response follow epithelial breast cancer patterns. 1

Surgical Management

• Perform modified radical mastectomy or breast-conserving surgery with axillary lymph node assessment (sentinel node biopsy or axillary dissection), following standard breast cancer surgical principles. 2, 3, 4
• Breast-conserving surgery is acceptable when adequate margins can be achieved relative to tumor size and breast volume. 2, 3
• Axillary staging is required (unlike true breast sarcomas where it is not performed). 1
• Complete surgical excision with negative margins is the cornerstone of local control. 2, 3, 4

Adjuvant Systemic Therapy

• Administer adjuvant chemotherapy for node-positive disease or large tumors (≥5 cm), as chemotherapy significantly improves outcomes in these high-risk subgroups. 2
• Most metaplastic carcinomas are triple-negative (85% hormone receptor-negative), so treat according to triple-negative breast cancer protocols. 3, 5, 1
• For the minority with hormone receptor-positive disease (15%), endocrine therapy should be offered following standard breast cancer guidelines. 3, 4
• Chemotherapy regimens should follow standard breast cancer protocols, not sarcoma regimens. 1

Adjuvant Radiation Therapy

• Deliver postoperative radiation therapy for tumors ≥5 cm or when >4 lymph nodes are involved, as RT significantly improves both disease-free and overall survival in these high-risk patients. 2
• Radiation therapy is a critical component of multimodality treatment for locally advanced disease. 2, 3
• Standard breast/chest wall and regional nodal radiation fields should be used as per breast cancer protocols. 2

Metastatic Disease Management

• For metastatic disease, use systemic chemotherapy as first-line treatment (since most are triple-negative), but expect poor response rates with median overall survival of only 3.4 months. 5
• Response to palliative chemotherapy is disappointingly poor: only 6% achieve partial response and 18% stable disease. 5
• The lungs are the most common site of first distant recurrence, unlike typical breast cancers. 3, 5
• For the rare hormone receptor-positive metastatic cases, endocrine therapy should be attempted first unless visceral crisis mandates immediate cytoreduction. 1, 6

Prognostic Factors and Risk Stratification

• Large tumor size (median 9 cm at presentation) and lymph node metastases are the strongest predictors of poor outcome. 2, 3, 4
• Mixed epithelial-mesenchymal histology (versus purely epithelial metaplasia) confers worse prognosis. 5
• Despite low rates of nodal involvement (82% node-negative), the disease remains highly aggressive with 5-year disease-free survival of only 52-63% and overall survival of 60-61%. 2, 5
• High local recurrence rates occur with median time to relapse of 12 months. 3, 4

Critical Pitfalls to Avoid

• Do not refer these patients to sarcoma centers for sarcoma-based treatment—this is the single most important error to avoid. 1
• Do not omit axillary staging, as nodal status is a critical prognostic factor requiring appropriate systemic therapy. 2, 3
• Do not withhold chemotherapy in node-positive or large tumor cases based on the assumption that "sarcomatous" features make it chemoresistant—chemotherapy does improve outcomes in these subgroups. 2
• Do not skip radiation therapy for locally advanced disease (≥5 cm or >4 positive nodes), as it significantly impacts survival. 2
• Recognize that metastatic disease has exceptionally poor prognosis despite aggressive treatment, requiring early palliative care discussions. 5