Is axillary lymph node (ALN) dissection performed in patients undergoing breast-conserving surgery (BCS) for breast cancer?

Axillary Lymph Node Dissection in Breast-Conserving Surgery

For patients undergoing breast-conserving surgery (BCS) with clinically negative axilla, sentinel lymph node biopsy (SLNB) alone is the standard of care, and completion axillary lymph node dissection (ALND) is NOT routinely performed—even when 1-2 sentinel nodes are positive—provided the patient receives whole-breast radiation therapy. 1

Standard Approach for Clinically Node-Negative Disease

• SLNB is the primary axillary staging procedure for patients with clinical stage I or II breast cancer and clinically negative axillary lymph nodes at diagnosis 1
• An experienced sentinel lymph node team is mandatory for proper execution of SLNB 1
• When sentinel nodes are negative on hematoxylin-eosin (H&E) staining, no further axillary surgery is required 1

When ALND Can Be Safely Omitted Despite Positive Sentinel Nodes

The landmark ACOSOG Z0011 trial fundamentally changed axillary management in BCS patients. This randomized trial compared SLNB alone versus completion ALND in women with T1/T2 tumors and fewer than 3 positive sentinel nodes undergoing breast-conserving surgery with whole-breast radiation 1

Key Z0011 Trial Results:

• At median follow-up of 6.3 years, locoregional recurrence rates were 2.8% (SLNB alone) versus 4.1% (ALND), showing no significant difference (P=0.11) 1
• Overall survival was approximately 92% in both groups 1
• At 10-year follow-up, overall survival remained noninferior between groups 2

Specific Criteria for Omitting ALND After Positive SLNB:

Based on Z0011 eligibility, ALND is NOT required when ALL of the following are met: 1, 2

• T1 or T2 tumor (≤5 cm clinically)
• 1 to 2 positive sentinel lymph nodes (macrometastases)
• Breast-conserving surgery performed
• Whole-breast radiation therapy planned
• No neoadjuvant therapy received
• Clinically negative axilla (no palpable adenopathy)

For sentinel node micrometastases (0.2-2.0 mm), ALND can also be safely omitted, as demonstrated by the IBCSG 23-01 trial showing no difference in disease-free survival between ALND and SLNB alone 1, 2

When ALND IS Still Indicated in BCS Patients

Completion ALND remains necessary in the following scenarios: 1

• Clinically positive nodes at diagnosis confirmed by fine-needle aspiration (FNA) or core biopsy
• Sentinel nodes cannot be identified during mapping
• More than 2 positive sentinel nodes on final pathology 2
• Patients not receiving whole-breast radiation therapy (though axillary radiation may substitute for ALND in select cases) 1

Technical Requirements for ALND When Performed:

• At least 10 lymph nodes should be removed for accurate pathologic staging 1
• Dissection includes level I and II nodes (tissue inferior to axillary vein from latissimus dorsi laterally to medial border of pectoralis minor) 1
• Level III dissection only if gross disease apparent in level II nodes 1

Recent Evidence Supporting Further De-escalation

Two major 2025 trials (SOUND and INSEMA) demonstrated that SLNB can be omitted entirely in highly selected BCS patients: 1

SOUND Trial Criteria for Omitting All Axillary Surgery:

• Tumor ≤2 cm
• Negative preoperative axillary ultrasound (or single suspicious node negative by FNA)
• 5-year distant disease-free survival was equivalent (no difference in local-regional relapse: 1.6% vs 1.7%) 1

INSEMA Trial Criteria:

• Clinical T1 or T2 (≤5 cm) invasive breast cancer
• Clinically node-negative
• Breast-conserving surgery planned
• 5-year invasive disease-free survival: 91.9% (no axillary surgery) vs 91.7% (SLNB), confirming noninferiority 1

However, these populations were predominantly postmenopausal with hormone receptor-positive, HER2-negative disease, and patients with high-risk features (grade 3, triple-negative, HER2-positive, age <50) were underrepresented. 1

Critical Pitfalls to Avoid

• Do not perform routine cytokeratin immunohistochemistry to define node involvement; treatment decisions should be based solely on H&E staining, as cytokeratin IHC positivity alone (with H&E-negative nodes) does not improve survival (ACOSOG Z0010 trial) 1
• Do not extrapolate Z0011 results to mastectomy patients—the trial specifically enrolled only BCS patients receiving whole-breast radiation 1
• Verify that whole-breast radiation is actually planned before omitting ALND in sentinel node-positive patients 1
• Confirm the exact number of positive sentinel nodes—if 3 or more are positive, ALND is still indicated 2

Morbidity Considerations

The primary rationale for avoiding ALND is reduction in surgical morbidity: 2

• Lymphedema rates: 2.6% with SLNB alone versus 27% with ALND
• Lower rates of arm/shoulder mobility restriction, sensory loss, and chronic pain with SLNB compared to ALND 1, 2

Historical Context

The de-implementation of routine ALND has been gradual but substantial: 1

• In 1998, only 6.1% of SLN-positive patients received SLNB alone
• By 2009, this increased to 23.0%
• By 2011,56.0% received SLNB alone
• By 2014, only 21.6% of invasive breast cancer patients underwent ALND (down from 35.4% in 2007) 1