Lymphatic Drainage Pathways
The breast drains lymph through several pathways. The primary pathway — carrying approximately 75% of lymph — is lateral and superior, draining to axillary lymph nodes (in the armpit). There are five levels of axillary lymph nodes relevant to breast surgery. Secondary pathways drain to internal mammary nodes (along the sternum), infraclavicular nodes, and contralateral axillary nodes. The nipple-areola complex has its own specific drainage patterns. Understanding these pathways is essential for breast cancer staging.
Sentinel Lymph Node Biopsy
The sentinel lymph node is the first lymph node(s) to receive drainage from the primary tumour. Sentinel lymph node biopsy (SLNB) is a minimally invasive staging technique that injects a tracer (radioactive colloid, blue dye, or both) near the tumour, then identifies and removes only the first draining node(s) for pathological examination. If the sentinel node is cancer-free, the remaining axillary nodes are very likely cancer-free, sparing the patient a full axillary dissection with its higher complication rate.
Impact of Surgery on Lymphatics
Axillary lymph node dissection (ALND) — historically performed in all breast cancer surgeries — carries significant risks to the lymphatic system, primarily lymphoedema of the arm. The development of SLNB has largely replaced ALND for early-stage disease, dramatically reducing lymphoedema rates. Cosmetic breast surgery generally has less impact on lymphatic drainage than oncological surgery but can affect lymphatic pathways if surgery involves the axillary region.
Implications for Implants
Large implants can alter lymphatic drainage patterns by compressing or displacing lymphatic channels. The clinical significance is not fully characterised but is an area of ongoing research. Seroma formation (a common complication of breast surgery) partly reflects disruption of lymphatic channels during pocket creation.
