Definitions

• Pyramidal space between upper lateral chest, medial arm, and directly inferior to shoulder joint
  • Contains fat, axillary artery and vein, brachial plexus, and axillary lymph nodes
  • Apex: Points to base of neck between anterior and middle scalene muscles
  • Base: Faces outward and is formed by skin and fascia between pectoralis major and latissimus dorsi
  • Anterior: Pectoralis major and minor muscles
  • Posterior: Subscapularis muscle on top portion; latissimus dorsi and teres major muscle on bottom
  • Inner wall: First 4 ribs and serratus magnus muscle
  • Outer wall: Convergence of anterior and posterior boundaries and humerus and biceps muscle
• Contents
  • Axillary vessels, brachial plexus, fat, loose connective tissue, axillary nodes, and possible vestigial breast glandular tissue
  • Axillary artery: Continuation of subclavian artery starting at border of 1st rib and terminating at border of latissimus dorsi where it becomes brachial artery
  • Lateral thoracic artery: Branch of axillary artery that travels at lower border of pectoralis minor muscle
  • Axillary vein: Projects medial and inferior to axillary artery; venous branches parallel arterial branches
• Fascia
  • Superficial layer (pectoral fascia composed of fascia from pectoralis major and minor muscles)
  • Deep layer (clavipectoral or costocoracoid fascia) extending from clavicle to base of axilla
• Nerves
  • Medial, lateral, and posterior cords of brachial plexus associated with and named for their relationship to axillary artery
    • Branches of brachial plexus: Long thoracic nerve and intercostobrachial nerve
    • Prone to injury during axillary dissection

Imaging Recommendations

Clinical Importance

Defined by Location of Metastatic Nodes Relative to Pectoralis Minor Muscle