Biology of lymphatic metastases in breast cancer: Lessons learned from sentinel node biopsy

Background: The evolution of sentinel node biopsy has placed new emphasis on the biology of lymphatic metastases in breast cancer. If radiocolloid mimics the migration of tumor cells, the nodes with the most uptake should also be the most likely to harbor metastatic cells. We attempted to correlate the frequency of metastatic disease to the greatest gamma uptake and to clarify the physiology of breast lymphatic drainage. Methods: Data were collected from 152 patients undergoing sentinel node biopsy from January 1997 to June 1999. Localization was by injection of unfiltered Tc-99m-labeled sulfur colloid. Sentinel nodes were identified with an intraoperative gamma counter and the 10% rule. A completion level I/II axillary dissection was performed in all patients. Results: Fifty-four of 152 patients were positive for metastatic disease. There were no false-negative sentinel nodes. In 46 (85%) of 54 cases, the node with the highest uptake was positive for metastatic disease. In the remaining eight (15%) cases, another node with a lower gamma count was positive. Conclusions: The sentinel node with the highest uptake is not the one that contains metastatic disease in 15% of cases. This may reflect variations in lymphatic channels or technical variations in colloid properties and injection technique.