What vessels and nerves are at risk in the axilla during a sentinel lymph node (SLN) biopsy for a breast lumpectomy?

Vessels and Nerves at Risk During Sentinel Lymph Node Biopsy in the Axilla

During sentinel lymph node biopsy (SLNB) for breast cancer, the primary vessels and nerves at risk in the axilla include the long thoracic nerve, thoracodorsal nerve, medial pectoral nerve, intercostal brachiocutaneous nerve, and the axillary vein. 1

Key Anatomical Structures at Risk

Nerves at Risk

• Long thoracic nerve: Injury can lead to serratus anterior muscle weakness causing scapular winging
• Thoracodorsal nerve: Supplies the latissimus dorsi muscle; damage may affect shoulder function
• Medial pectoral nerve: Innervates the pectoralis muscles; injury may weaken chest wall
• Intercostal brachiocutaneous nerve: Provides sensory innervation to the posterior upper arm; damage results in numbness 1

Vascular Structures at Risk

• Axillary vein: Excessive manipulation or stripping increases lymphedema risk
• Thoracodorsal vessels: Important for potential future reconstruction, particularly if free TRAM flap reconstruction might be needed 2

Surgical Considerations

Incision Placement

• The breast incision and axillary incision should be separate to avoid unnecessary deformity
• A transverse incision in the low axilla from just posterior to the pectoralis major border to the anterior border of the latissimus dorsi provides excellent exposure with good cosmetic results
• Alternatively, a vertical incision posterior and parallel to the pectoralis major border can be used 1

Technical Aspects

• Preservation of the identified nerves is essential to minimize post-operative morbidity
• Careful handling of the axillary vein is necessary as stripping increases lymphedema risk
• Closed suction drainage is typically advisable after the procedure 1

Morbidity Considerations

Despite being less invasive than complete axillary lymph node dissection (ALND), SLNB still carries risk of upper limb morbidity:

• Pain
• Reduced range of motion in forward flexion, abduction, and external rotation
• Decreased strength in shoulder abductors and elbow flexors
• Perceived disability in activities of daily living 3

Importance of Surgical Experience

The success and safety of SLNB depends significantly on surgical expertise:

• An experienced sentinel lymph node team is mandatory for accurate mapping and excision 1
• Surgeons should have a low threshold to convert to ALND when:
  • The SLNB procedure is technically unsatisfactory
  • Clinically suspicious nodes are present after removal of all sentinel nodes 1
  • Mapping fails (occurs in approximately 5.6% of cases) 1

Evolving Practices

The transition from ALND to SLNB has influenced reconstruction practices:

• Increased use of internal mammary vessels rather than thoracodorsal vessels for free flap reconstruction
• This shift reflects concern that subsequent axillary surgery might injure thoracodorsal vessels if they were used in reconstruction 2

SLNB has become the standard of care for axillary staging in clinically node-negative breast cancer patients, offering comparable survival outcomes to ALND with reduced morbidity when performed by experienced surgeons with proper patient selection 4.