Tumor Characteristics Influencing Non-Sentinel Lymph Node Involvement in Clinically Node Negative Patients with Breast Cancer

PURPOSE: The negative sentinel lymph node (SLN) biopsy avoids conventional axillary dissection in patients with breast cancer with clinically negative axilla. Despite negative SLN, there is a risk of leaving involved non-SLN behind in the axilla. We investigated the predictive power of tumor characteristics for non-SLN metastasis. METHODS: Lymphatic mapping with blue dye method for SLN biopsy and level 1-2 axillary dissections were performed to establish axillary status in 59 patients with T1 and T2 breast cancer and clinically negative axilla. Tumor's characteristics were histopathologically established to assess their association with non-SLN metastasis. RESULTS: The axilla was malignant in 23 (39%) patients. The SLN alone was metastatic in 10, both SLN and non-SLN in 9, and non-SLN alone in 4 (7%) patients. The false negative rate for SLN biopsy was 10% in our series. The rate of positive non-SLN was found as 0% in T1a-b, 19% in T1c, and 40% in T2 tumors (p=0.035). Lymphovascular invasion was positive in 14 (61%) patients with axillary metastasis (p<0.001), and in 10 (77%) patients with non-SLN involvement (p<0.001). CONCLUSION: We concluded that there was a small risk of involved non-SLN despite negative SLN. Tumor size (near or greater than 2 cm) was significantly associated with non-SLN metastasis. Peritumoral lymphovascular invasion was a positive predictor of the metastatic involvement in non-SLNs.