Lymphatics of the breast and the rationale for different injection techniques.

Recent studies suggest that the sentinel lymph node in the axilla can be identified no matter where the tracer is administered in the breast. Tracers injected in the skin or subareolar plexus may be the quickest to travel to the axilla but rarely identify sentinel nodes outside the axilla. Tracers administered in or around the tumor identify sentinel nodes in the axilla but also in the internal mammary chain, in the breast parenchyma, in between the pectoralis muscles, and in the supraclavicular fossa. Extra-axillary sentinel nodes can be seen in approximately 25% of the patients. Administration of the tracer in the breast parenchyma with pursuit of sentinel nodes both in the axilla and elsewhere provides more accurate staging in addition to preventing unnecessary axillary node dissections. This will lead to more accurate indications for both postoperative radiotherapy and adjuvant systemic treatment. Implications for the staging system should be considered as well.