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Axilla
Mohammad Eghtedari, MD, PhD; Wei Tse Yang, MBBS
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TERMINOLOGY

  • 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

ANATOMY IMAGING ISSUES

  • Imaging Recommendations

    CLINICAL IMPLICATIONS

    • Clinical Importance

      AXILLARY NODES: SURGICAL STAGING

      • Defined by Location of Metastatic Nodes Relative to Pectoralis Minor Muscle

        Selected References

        1. de Meric de Bellefon M et al: Management of the axilla in the era of breast cancer heterogeneity. Front Oncol. 8:84, 2018
        2. Grimm LJ et al: Normal axillary lymph node variability between white and black women on breast MRI. Acad Radiol. 25(3):305-8, 2018
        3. Jatoi I et al: Surgical management of the axilla in early breast cancer. Curr Probl Surg. 55(2):47-65, 2018
        4. Wai CJ: Axillary anatomy and history. Curr Probl Cancer. 36(5):234-44, 2012
        Related Anatomy
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        Related Differential Diagnoses
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        References
        Tables

        Tables

        TERMINOLOGY

        • 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

        ANATOMY IMAGING ISSUES

        • Imaging Recommendations

          CLINICAL IMPLICATIONS

          • Clinical Importance

            AXILLARY NODES: SURGICAL STAGING

            • Defined by Location of Metastatic Nodes Relative to Pectoralis Minor Muscle

              Selected References

              1. de Meric de Bellefon M et al: Management of the axilla in the era of breast cancer heterogeneity. Front Oncol. 8:84, 2018
              2. Grimm LJ et al: Normal axillary lymph node variability between white and black women on breast MRI. Acad Radiol. 25(3):305-8, 2018
              3. Jatoi I et al: Surgical management of the axilla in early breast cancer. Curr Probl Surg. 55(2):47-65, 2018
              4. Wai CJ: Axillary anatomy and history. Curr Probl Cancer. 36(5):234-44, 2012