Characteristics of the sentinel lymph node in breast cancer predict further involvement of higher-echelon nodes in the axilla - A study to evaluate the need for complete axillary lymph node dissection

Background: Sentinel lymph node (SLN) biopsy techniques provide accurate no dal staging for breast cancer. In the past, complete lymph node dissection (CLND) (levels 1 and 2) was performed for breast cancer staging, although t he therapeutic benefit of this more extensive procedure has remained contro versial. Hypothesis: It has been demonstrated that if the axillary SLN has no eviden ce of micrometastases, the non-sentinel lymph nodes (NSLNs) are unlikely to have metastases. Objective: To determine which variables predict the probability of NSLN inv olvement in patients with primary breast carcinoma and SLN metastases. Methods: An analysis of 101 women with SLN metastases and subsequent CLND w as performed. Variables included size of the primary tumor, tumor volume in the SLN, staining techniques used to initially identify the micrometastase s (cytokeratin immunohistochemical vs hematoxylin-eosin), number of SLNs ha rvested, and number of NSLNs involved with the metastases. Tumor size was d etermined by the invasive component of the primary tumor. Patients with duc tal carcinoma in situ who were upstaged with cytokeratin staining were cons idered to have stage T1a tumors. Results: Sentinel lymph node micrometastases (<2 mm) detected initially by cytokeratin staining were associated with a 7.6% (2/26) incidence of positi ve CLND compared with a 25% (5/20) incidence when micrometastases were dete cted initially by routine hematoxylin-eosin staining. Sentinel lymph node m icrometastases, regardless of identification technique, inferred a risk of 15.2% (7/46) for NSLN involvement. As the volume of tumor in the SLN increa sed (ie, <2 mm, >2 mm, grossly visible tumor), so did the risk of NSLN meta stases (P<.001). Conclusions: Our study demonstrated that patients with micrometastases dete cted initially by cytokeratin staining had low-volume disease in the SLN wi th a small chance of having metastases in higher-echelon nodes in the regio nal basin other than the SLN. Characteristics of the SLN can provide inform ation to determine the need for a complete axillary CLND. Complete lymph no de dissection may not be necessary in patients with micrometastases detecte d initially by cytokeratin staining since the disease is confined to the SL N 92.4% of the time. However, the therapeutic value of CLND in breast cance r remains to be determined by further investigation.