Residency · Residency · General Surgery
Axillary Management in Breast Cancer
Overview
Axillary lymph node status is the single most important prognostic factor in early breast cancer. Surgical management of the axilla has evolved dramatically from routine axillary lymph node dissection to selective sentinel lymph node biopsy and, increasingly, toward further de-escalation. The key paradigm shift is the recognition that removing positive nodes does not necessarily improve survival, as systemic therapy and radiation effectively address micrometastatic disease.
Axillary Anatomy
The axillary lymph nodes are divided into three levels defined by their relationship to the pectoralis minor muscle. Level I nodes are lateral to the pectoralis minor. Level II nodes are posterior to the pectoralis minor. Level III nodes, also called the apical or infraclavicular nodes, are medial to the pectoralis minor. Rotter's (interpectoral) nodes lie between the pectoralis major and minor. Standard axillary lymph node dissection removes levels I and II. Lymphatic drainage generally follows an orderly pattern from level I to II to III, and skip metastases are rare, occurring in less than 2% of cases.
Sentinel Lymph Node Biopsy (SLNB)
Concept
The sentinel lymph node is the first node to receive lymphatic drainage from the tumor. If it is negative, the remaining axillary nodes are very likely negative, with a false-negative rate of less than 5-10%. This approach has been validated by the NSABP B-32, Milan Sentinel Node, and ALMANAC trials.
Technique
The dual-tracer technique combines a radiocolloid (technetium-99m sulfur colloid or nanocolloid) with a blue dye (isosulfan blue or methylene blue). The radiocolloid is injected 1-24 hours preoperatively via subareolar, periareolar, or peritumoral routes and is detected intraoperatively with a gamma probe. Blue dye is injected at the time of surgery and visually identifies blue nodes and lymphatic channels. The dual-tracer approach achieves an identification rate exceeding 95%. Indocyanine green (ICG) fluorescence is an emerging alternative or adjunct detected using a near-infrared camera. Magnetic tracer (Magtrace/Sentimag) uses iron oxide nanoparticles as a non-radioactive alternative. Typically 1-3 sentinel nodes are identified, and all hot and blue nodes plus any clinically suspicious nodes should be removed.
Intraoperative Assessment
Options for intraoperative assessment include touch preparation cytology, frozen section, or one-step nucleic acid amplification (OSNA). These allow immediate axillary lymph node dissection if the sentinel node is positive, though this is performed less frequently given the de-escalation trend driven by the Z0011 trial. Intraoperative assessment is largely being abandoned for early-stage disease.
Pathologic Assessment
Standard pathologic assessment uses H&E staining, with immunohistochemistry for cytokeratin to detect micrometastases and isolated tumor cells. Findings are classified as macrometastasis (greater than 2 mm), micrometastasis (0.2-2 mm, staged as pN1mi), or isolated tumor cells (less than 0.2 mm or fewer than 200 cells, staged as pN0(i+)). Isolated tumor cells are not considered node-positive.
<image>Sentinel lymph node biopsy technique showing dual-tracer injection, intraoperative gamma probe detection, and identification of blue-stained sentinel node in the axilla</image>
Indications for SLNB
Sentinel lymph node biopsy is indicated for clinically node-negative invasive breast cancer (T1-T3), for DCIS undergoing mastectomy (since SLNB cannot be performed after mastectomy if invasive cancer is found), and for DCIS with a high risk of occult invasion (large, high-grade, or associated with a palpable mass).
Contraindications to SLNB (Requiring ALND)
Contraindications to SLNB include inflammatory breast cancer, clinically node-positive disease confirmed by FNA or CNB (unless the patient has received neoadjuvant chemotherapy with a nodal response), and prior extensive axillary surgery (a relative contraindication).
Management of the Positive Sentinel Node
ACOSOG Z0011 Trial (Landmark)
The ACOSOG Z0011 trial enrolled patients with T1-T2 invasive breast cancer and 1-2 positive sentinel nodes undergoing BCS with whole-breast radiation and randomized them to SLNB alone versus completion ALND. At 10 years, there was no difference in local recurrence, disease-free survival, or overall survival. The conclusion is that ALND can be safely omitted for patients meeting Z0011 criteria: T1-T2 tumor, 1-2 positive sentinel nodes with macro- or micrometastases, planned BCS, planned whole-breast radiation, no matted or grossly positive nodes, and no preoperative chemotherapy.
AMAROS Trial
The AMAROS trial enrolled patients with T1-T2 tumors and a positive sentinel node and randomized them to completion ALND versus axillary radiation therapy. It demonstrated equivalent regional control with less lymphedema in the radiation arm. This trial supports axillary radiation as an alternative to ALND for positive sentinel nodes and is applicable in both BCS and mastectomy settings.
SENOMAC Trial
The SENOMAC trial extended Z0011 findings to include patients with 1-2 macrometastatic sentinel nodes undergoing mastectomy. SLNB alone, without ALND or axillary radiation, was non-inferior, broadening the de-escalation of axillary surgery beyond the BCS population.
Micrometastases and Isolated Tumor Cells
The IBCSG 23-01 trial demonstrated no benefit from ALND for micrometastases in the sentinel node in patients undergoing BCS with whole-breast radiation. Isolated tumor cells (pN0(i+)) are staged as node-negative, and ALND is not recommended. Micrometastases (pN1mi) are treated as low-volume nodal disease, and ALND is generally omitted.
<image>Summary diagram of axillary management decision tree based on clinical nodal status, sentinel node biopsy results, and applicable trial data (Z0011, AMAROS, SENOMAC)</image>
Axillary Management After Neoadjuvant Chemotherapy (NAC)
Clinically Node-Negative Before NAC
For patients who are clinically node-negative before NAC, SLNB after NAC is standard, and its accuracy is comparable to SLNB performed before NAC.
Clinically Node-Positive Before NAC (Converted to Clinically Node-Negative)
SLNB after NAC is feasible in initially node-positive patients who convert to clinically node-negative, but an optimized technique is required to reduce the false-negative rate. This includes dual-tracer mapping, removal of a minimum of 3 sentinel nodes, and targeted axillary dissection (TAD), which involves placing a clip in the biopsy-proven positive node before NAC and removing the clipped node along with the sentinel nodes after NAC. The ACOSOG Z1071, SENTINA, and SN FNAC trials established the feasibility of this approach with acceptable false-negative rates when optimal technique is used. If pathologic complete response is achieved in the axilla (ypN0), no further axillary surgery is needed. If residual axillary disease is present, ALND or axillary radiation is indicated.
Targeted Axillary Dissection (TAD)
Targeted axillary dissection combines SLNB with removal of the previously clipped (marked) node. This approach reduces the false-negative rate to less than 2%, compared to 7-12% with SLNB alone, and is becoming the standard approach for initially node-positive patients after NAC.
Axillary Lymph Node Dissection (ALND)
Technique
ALND involves dissection of levels I and II, lateral and posterior to the pectoralis minor muscle. The boundaries are the axillary vein superiorly, the latissimus dorsi laterally, and the chest wall medially. The long thoracic nerve (which innervates the serratus anterior) and the thoracodorsal nerve and vessels (which supply the latissimus dorsi) must be preserved. The intercostobrachial nerve crosses the axilla and may need to be sacrificed, which causes numbness of the medial arm and axilla -- patients should be warned about this preoperatively. A minimum of 10 lymph nodes should be retrieved for adequate staging.
Indications (Current/Narrowing)
Current indications for ALND, which are progressively narrowing, include clinically node-positive disease confirmed by biopsy (when not receiving NAC), residual nodal disease after NAC, failed SLNB (inability to identify a sentinel node), 3 or more positive sentinel nodes (though even this threshold is being questioned), and inflammatory breast cancer.
Complications
Lymphedema is the most significant long-term morbidity, affecting 15-25% of patients, and the risk is lifelong. Risk is increased with radiation, obesity, infection, and removal of a greater number of nodes. Prevention strategies include avoiding blood draws and blood pressure measurement on the affected arm (traditional practice with limited evidence), early detection with perometry, and physical therapy. Seroma is the most common acute complication and is managed with aspiration. Numbness from intercostobrachial nerve injury occurs in 30-70% of patients. Shoulder dysfunction with limited range of motion requires physical therapy. Winged scapula from long thoracic nerve injury is rare but debilitating.
<image>Axillary anatomy during lymph node dissection showing levels I, II, and III nodes and the relationship to the pectoralis minor, long thoracic nerve, thoracodorsal nerve, and axillary vein</image>
De-escalation of Axillary Surgery -- Emerging Evidence
The trend in axillary management is toward less surgery, with radiation or observation replacing axillary dissection. Active trials include POSNOC, ALLIANCE A011202, and NSABP B-51/RTOG 1304. The future direction may involve clinical and imaging nodal assessment replacing surgical staging in select patients. Genomic assays such as Oncotype DX and MammaPrint increasingly inform systemic therapy decisions independent of nodal status.
Clinical Pearls
The Z0011 trial fundamentally changed axillary management, and most patients with 1-2 positive sentinel nodes undergoing BCS no longer need ALND. For initially node-positive patients receiving NAC, targeted axillary dissection (clipped node plus SLNB) reduces false-negative rates and may spare patients ALND if they achieve nodal pathologic complete response. SLNB should use the dual-tracer technique for optimal identification rates exceeding 95%. At least 3 sentinel nodes should be removed when performing SLNB after neoadjuvant chemotherapy in initially node-positive patients. Lymphedema is the most significant long-term morbidity of ALND and is the primary reason to avoid unnecessary axillary dissection. Isolated tumor cells (less than 0.2 mm) in sentinel nodes are staged as node-negative and do not warrant further axillary surgery. Axillary ultrasound with FNA or CNB of suspicious nodes preoperatively helps triage patients to SLNB versus NAC followed by targeted axillary dissection.
References
- Giuliano AE, et al. Effect of axillary dissection vs no axillary dissection on 10-year overall survival among women with invasive breast cancer and sentinel node metastasis: The ACOSOG Z0011 randomized clinical trial. JAMA. 2017;318(10):918-926.
- Donker M, et al. Radiotherapy or surgery of the axilla after a positive sentinel node in breast cancer (EORTC 10981-22023 AMAROS). Lancet Oncol. 2014;15(12):1303-1310.
- Boughey JC, et al. Sentinel lymph node surgery after neoadjuvant chemotherapy in patients with node-positive breast cancer: The ACOSOG Z1071 trial. JAMA. 2013;310(14):1455-1461.
- Caudle AS, et al. Improved axillary evaluation following neoadjuvant therapy for patients with node-positive breast cancer using selective evaluation of clipped nodes: Implementation of targeted axillary dissection. J Clin Oncol. 2016;34(10):1072-1078.
- de Boniface J, et al. Omitting axillary dissection in breast cancer with sentinel-node metastases (SENOMAC). N Engl J Med. 2024;390(13):1163-1175.
