Lymphatic mapping of the breast: Locating the sentinel lymph nodes

When the concept of sentinel lymph node biopsy was described in patients wi th melanoma, researchers quickly started to use lymphatic mapping technique s in breast cancer patients in an attempt to locate the sentinel node in th e axilla, We have been performing mammary lymphoscintigraphy in this role f or 6 years and have now studied 159 patients. Like others, we have found th at most breast cancers (93%) have lymphatic drainage that includes the axil la, and we have found an average of 1.4 axillary sentinel nodes in these pa tients. Surgical biopsy of the axillary sentinel nodes accurately staged th e node field in 96% of patients. We have also found, however, that the patt ern of lymphatic drainage from the cancer site is unpredictable; and in 49% of patients lymphatic drainage occurred across the center line of the brea st to axillary or internal mammary sentinel nodes. In more than half of our patients (56%) lymphatic drainage occurred to lymph nodes outside the axil la including the internal mammary (45%), supraclavicular (13%), and interpe ctoral and intramammary interval nodes (12%). These nodes are also sentinel nodes, and their presence indicates that a sentinel node biopsy procedure that stages only the status of the axillary lymph nodes has the potential t o understage about half the patients with breast cancer. High quality lymph oscintigraphy allows accurate mapping of peritumoral lymphatic drainage in most patients with breast cancer. It is possible that in the future accurat e nodal staging in each individual will involve biopsy of all sentinel lymp h nodes, regardless of their location.