Sentinel Lymph Node Total Tumoral Load as a Predictor of Non Sentinel Node Involvement in Early Breast Cancer

Inclusion Criteria: * Pathologically confirmed invasive breast carcinoma * Stage T1-3,N0 evaluated by physical exam or imaging according to AJCC v.7 and best clinical local practices * Intraoperative evaluation of sentinel lymph node (SLN) by OSNA * Complete dissection of axillary lymph nodes after the evaluation of the SLNs by OSNA * Pathology report of the tumor and dissected lymph nodes that includes the following information: * primary tumor size (mm), tumor grade (Scarff-Bloom Richardson), estrogen receptor status * progesterone receptor status * HER2 status (ASCO/CAP guidelines) * Ki67 index * presence/absence of lymphovascular invasion * total number of sentinel and non-sentinel lymph nodes dissected during surgery * total number of positive and negative sentinel and non-sentinel lymph nodes, \*size of the metastasis in both sentinel and non-sentinel lymph nodes * total tumoral load in each sentinel lymph node, expressed as number of CK19 mRNA copies per microliter. Exclusion Criteria: * Patients who underwent neoadjuvant chemotherapy * CK19-negative breast tumor * ALND with \<10 lymph nodes * In situ carcinoma only * Metastatic breast cancer at time of diagnosis