A prospective feasibility trial to determine the significance of the sentinel node gradient in breast cancer: a predictor of nodal metastasis location.

BACKGROUND: Sentinel lymph node (SN) biopsy is standard for breast cancer staging, but SN dye gradients and their significance have never been characterized. If predictive of SN metastasis location, their use for focused pathology examination might improve intraoperative imprint cytology sensitivity.
METHODS: This prospective trial enrolled clinically lymph node-negative patients with invasive breast cancer not undergoing neoadjuvant chemotherapy. Surgeons marked SN gradients at their bluest end. Nodal halves were examined separately by imprint cytology, and the marked SN half was correlated to metastasis location. Demographic, pathologic, and prognostic features were recorded.
RESULTS: Mean patient age and tumor size for the 102 patients was 59.6 years and 2.2 cm, respectively. Of 169 SNs, 159 (94.1%) had dye gradients, which varied by tumor quadrant, but not by histology, diagnosis method, grade, or stage. Among 41 marked SNs with metastases, 92.7% were present in the halves marked by the surgeon. Fourteen were confined to 1 nodal half, with 11 on the marked side and 3 on the unmarked side (P = .029). Metastases were smaller when confined to 1 versus both SN halves (0.14 vs 0.75 cm; P = .005), and smaller (0.87 vs 0.13 cm; P < .0001) when missed intraoperatively.
CONCLUSIONS: Dye gradients occur in most SNs and predict metastasis location. The smallest metastases are hardest to detect intraoperatively and are usually confined to the marked SN half. This suggests that marking an SN's bluest half warrants further study to explore whether its correlation to metastasis location may be exploited to focus pathologic examination and decrease the reoperative axillary dissection rate. (c) 2008 American Cancer Society