Expansion
Level I lateral to pectoralis minor, level II behind it, level III medial to it
Expansion
Pectoralis minor runs from ribs 3, 4 and 5 to the coracoid process, and its lower border divides the axillary nodes into three surgical levels:
- Level I - lateral to (below) pectoralis minor; the anterior, posterior and lateral groups
- Level II - behind pectoralis minor; the central group
- Level III - medial to (above) pectoralis minor; the apical group
Lymph then passes to the supraclavicular nodes and the subclavian lymph trunk.
Rotter’s (interpectoral) nodes lie between pectoralis major and minor and are a separate small group.
Spread is usually orderly from level I upwards, which is what makes sentinel node biopsy reliable. Skip metastases to a higher level without involvement of a lower one occur in only a small minority.