OBJECTIVES Multicentricity is not listed as a major prognostic parameter in invasive breast carcinoma, and is not by itself an indication of systemic adjuvant treatment. Furthermore, evaluating the size of these tumors is discussed. The aims of this study are to evaluate prognostic value of multicentricity, and to compare different way for measuring multicentric breast carcinomas. PATIENTS AND METHODS Between 2001 and 2008, 1458 patients having breast invasive carcinoma were included in Tenon Hospital, Paris, France; 16% had a multicentric cancer. We have compared impact of multicentricity on lymph node (LN) involvement, and compared 3 ways for measuring these cancers. RESULTS LN involvement was significantly associated with multicentricity. We found an over-risk of 20% for LN involvement in patients having multicentric cancer, whatever the size of the tumors. Considering the diameter of the largest focus is the best way for measuring these cancers. DISCUSSION AND CONCLUSION We did not find a subgroup of patients at low risk of LN involvement when having a multicentric breast cancers. These results lead us to extend indications of adjuvant chemotherapies in all multicentric breast cancer. These results should be validated by randomized prospective studies.