A 48-year-old Indian woman with T2N1M0 invasive lobular carcinoma of the breast is counselled about surgical options. Which feature best distinguishes a candidate for breast-conserving therapy (BCT) from one requiring mastectomy?

Explanation

## BCT vs Mastectomy: The Discriminating Criterion ### Indications for Breast-Conserving Therapy (BCT) **Key Point:** BCT is appropriate when: 1. **Negative surgical margins can be achieved** (typically ≥1 mm, preferably ≥2 mm) 2. **Acceptable cosmetic outcome** is anticipated 3. **Radiotherapy is feasible and acceptable** to the patient 4. **No absolute contraindications** exist (pregnancy, prior breast radiotherapy, diffuse microcalcifications) ### Indications for Mastectomy **Key Point:** Mastectomy is required when: - Negative margins cannot be achieved despite adequate excision - Patient refuses radiotherapy - Pregnancy (radiotherapy contraindicated) - Prior breast radiotherapy - Multicentric disease (tumors in different quadrants) - Diffuse suspicious microcalcifications ### Critical Comparison | Criterion | BCT-Suitable | Mastectomy-Required | | --- | --- | --- | | **Margin status** | Negative margins achievable | Cannot achieve negative margins | | **Cosmesis** | Acceptable | Poor cosmesis expected | | **Radiotherapy** | Feasible and acceptable | Contraindicated or refused | | **Tumor size** | Relative (not absolute) | Not primary criterion | | **Node status** | N0, N1, N2 all eligible | Not a primary criterion | | **Histology** | All types eligible | Not a primary criterion | **High-Yield:** **Margin status and radiotherapy feasibility** are the true discriminators — not tumor size, nodal status, or histology. A T4 tumor can be treated with BCT if margins are negative and radiotherapy is given; conversely, a small T1 tumor requires mastectomy if margins cannot be cleared. **Clinical Pearl:** The patient in this stem has T2N1M0 disease — **N1 involvement does NOT preclude BCT**. She is a candidate for BCT if margins are negative and radiotherapy is planned. This is a common misconception in clinical practice. **Mnemonic:** **MARC** = **M**argins negative, **A**cceptable cosmesis, **R**adiotherapy feasible, **C**ontraindications absent → BCT eligible