Ki-67 immunostaining activity is higher in positive axillary lymph nodes than in the primary breast tumor

Background. The monoclonal antibody Ki-67 allows to investigate the proliferative activity of tumor and is a clinically useful marker to characterize breast cancer. In this study, we have compared Ki-67 activity in 38 primary breast tumors and in their respective positive axillary lymph nodes (ALNs). Methods. Immunohistochemistry with the monoclonal antibody against Ki-67 was performed in 38 nodes positive breast carcinomas and in their respective positive ALNs. Statistical analysis was performed with the Student's t-test (2-tailed) for equality of means. Results. The proliferation index measured by Ki-67 expression was significatively higher (p < 0.02) in ALN than in the primary tumor (29.8% v.s. 21.8%). Conclusion. These results strongly suggest a higher proliferation and perhaps aggressivity of metastatic neoplastic cells when compared with their respective primary tumor. Perhaps, in the future, these differences in proliferation behavior might be taken into account when considering the choice of the adjuvant therapy.