We found OSNA to be very helpful for the intra-operative determination of the tumor load of a SLN as a basis for decision-making concerning further surgical axillary intervention. OSNA allows precise differentiation of micro- from macrometastasis, and the CK19 copy number predicts the probability of tumor load in other axillary lymph nodes and might help to find adequate adjuvant treatment options. This objective method is well suitable for everyday use and may reduce the pathologic workload and the risk of secondary operative interventions with all associated costs and stress for the patients.