Factors influencing the number of sentinel lymph nodes identified in patients with breast cancer

Background Although the sentinel lymph node (SLN) is defined as the first node draining a tumor, multiple nodes are often identified. Few SLNs are required for adequate staging; removal of more may be unnecessary. The objective of this study was to determine factors influencing the number of SLN identified. Methods The University of Louisville Breast Sentinel Lymph Node Study was used to determine correlates of identifying greater than 4 SLNs by using univariate and multivariate analyses. Results An SLN was identified in 3,882 of 4,131 patients (94%). The median number of SLN identified was 2 (range 1–18); 90% had ≤4 SLNs identified. Palpable tumors, surgeon inexperience, and dermal injection were associated with greater than 4 SLNs identified. All 3 of these factors remained significant on multivariate analysis. Conclusions Palpable tumors often have greater than 4 SLNs identified, and the use of intradermal injection increases this probability.