Lymphatic drainage of the breast

Lymphatic drainage of breast originates from breast lobules and flows through intramammary nodes and channels into a subareolar plexus, called Sappey’s plexus. From this plexus, lymphatic drainage takes place through three main routes that parallel venous tributaries. Lymphatics from the left breast ultimately terminate in the thoracic duct and the left subclavian vein, and from the right breast in the right subclavian vein. 

• axillary or lateral pathway
  • dominant pathway (receives >75% of lymph from breasts)
  • drains lateral quadrants of breast either directly or via Sappey's plexus to axillary nodes 
  • either runs around inferior border of pectoralis major to reach the pectoral group of lymph nodes or pass directly to the subscapular group
  • few channels from superior breast to the apical group sometimes interrupted by the infraclavicular group of lymph nodes 
• internal mammary pathway
  • originates from both the medial and lateral quadrants of the breast
  • passes through the intercostal spaces and pectoralis major into parasternal/internal mammary lymph nodes
  • connections may lead across the median plane and hence to the contralateral breast
• retromammary pathway
  • comes from the deeper portion of the breast
  • drains to the subclavicular plexus

Other pathways occur when usual channels are blocked in disease. Lymph may pass to the contralateral breast, cervical nodes, peritoneal cavity and liver through the diaphragm or through the rectus sheath.

Axillary lymph nodes can be divided into surgical levels:

• level 1: lying below pectoralis minor
• level 2: lying behind pectoralis minor
• level 3: lying between the upper border of pectoralis minor and lower border of the clavicle