Axillary sentinel lymph nodes in breast cancer: a single lymphatic pathway drains the entire mammary gland

Aim To report the pattern of lymphatic mapping following intrasubdermal injections of radiocolloid and of blue dye in different sites of the breast. Methods Prior to surgery 137 breast cancer patients underwent intrasubdermal injection of 30–50 MBq 99mTc-colloidal albumin over the tumour site (ISI group). Ten minutes before surgery, 2 ml patent blue was injected in the subareolar area (SAI group) in 117/137 patients, while 20 patients received intrasubdermal blue-dye in the quadrant opposite the tumour site (OQI group). The different injection routes were considered concordant when the hottest sLN was also blue. Results In 134/137 patients radiocolloid drained to one or more axillary nodes, while blue nodes were found in 98/117 SAI patients and in 17/20 OQI patients. Multiple hot nodes were found in 63/134 cases and multiple blue nodes in 35/115. In patients in whom both tracers reached the axilla, the hottest node was also blue in 108/115 cases (93/98 SAI and 15/17 OQI patients). In the seven discordant cases, the hottest node was not blue, but in two cases the blue node was also radioactive. Conclusions Superficial lymphatic drainage from the breast most frequently merges to a single axillary lymph node, irrespective of the site of tracer injection. In a few cases different injection sites identify different, often closely interconnected sLNs.