Breast Anatomy and FAQs

Ambroise Paré (1510-1590) never described a specific surgery for breast cancer, but he wrote about the importance lymphatics play in the spread of breast cancer. The precedence for the first modern mastectomy was by Jean Louis Petit (1674-1750). Since that time, there have been a wide range in how breast surgery is approached. Halsted radical mastectomy was first performed in 1882 by William S. Halsted. With the advent of neoadjuvant and adjuvant therapies, lumpectomy and modified radical mastectomies have become the most common surgical options utilized today.

Anatomy

• Risk of a female in the U.S. developing breast cancer in her lifetime is 12.3%
• Majority of breast cancers are diagnosed after an abnormal screening mammogram
• Breast borders
  • Superior: clavicle
  • Inferior: inframammary fold
  • Medial: sternum
  • Lateral: latissimus dorsi
• Axillary borders
  • Anterior: pectoralis minor, pectoralis major
  • Superior: axillary vessels, clavicle, scapula, rib 1
  • Medial: serratus anterior, ribs 1-4
  • Lateral: humerus, coracobrachialis, short head of biceps brachii
  • Posterior: latissimus dorsi, subscapularis, teres major
• Breast blood supply
  • Internal thoracic (mammary): 2nd, 3rd, 4th perforating arteries
  • Lateral thoracic
  • Thoracoacromial
  • Posterior intercostal arteries: 2nd, 3rd, 4th
• Principal blood supply to the breast enters the breast superolaterally (axillary artery branches) and superomedially (internal thoracic branches)
• Batson’s plexus → valveless veins that drain to vertebral blood supply
• Lymph node levels
  • Level I: lateral to pectoralis minor
  • Level II: beneath pectoralis minor
  • Level III: medial to pectoralis minor
  • Level I and II are targets for axillary dissection
• Rotter’s nodes
  • Group of small lymph nodes located between pectoralis major and pectoralis minor
  • Level II lymph nodes
• Axillary tail of Spence → extension of breast tissue into the axilla
• Breast innervation
  • Lateral cutaneous branches of intercostal nerves 3, 4, 5
    • Approaches from lateral to medial
  • Anterior cutaneous branches of intercostal nerves 3, 4, 5
    • Approaches from medial to lateral
• Nerves
  • Long thoracic nerve
    • Innervates serratus anterior (lateral thoracic a. supplies serratus anterior)
    • Injury → winged scapula
  • Thoracodorsal nerve
    • Innervates latissimus dorsi thoracodorsal a. supplies latissimus dorsi)
    • Injury → weak arm pull-ups and adduction 
  • Medial pectoral nerve
    • Innervates pectoralis major and pectoralis minor
    • Passes through pectoralis minor in 60% of patients and passes laterally around pectoralis minor in 40% of patients as it travels to innervate the lower region of the pectoralis major
    • Arises from medial cord of brachial plexus
  • Lateral pectoral nerve
    • Innervates pectoralis major
    • Dominant lateral nerve to pectoralis major muscle arises from lateral cord and passes medial to pectoralis minor near its insertion; closely associated with acromial thoracic artery
  • Intercostobrachial nerve (lateral cutaneous branch of 2nd intercostal nerve)
    • Provides sensation to medial arm and axilla
    • Located just below axillary vein during axillary dissection
    • Can transect without serious complications
    • Most common injured nerve in modified radical mastectomy or axillary lymph node dissection

FAQs