Ki-67 expression in axillary lymph node metastases in breast cancer is prognostically significant

Several studies have documented the prognostic significance of cell proliferation in breast cancer and its positive relationship with tumor grade, size, mitotic activity, hormonal and Her-2 status, and tumor progression. The Ki-67 antigen provides an accurate measure of the growth fraction of a tumor. Ki-67 expression in 103 primary breast carcinomas and their corresponding axillary lymph node metastases was correlated with age, tumor grade, size, estrogen receptor (ER), progesterone receptor (PgR), p53, epidermal growth factor receptor (EGFR), Bcl-2, Her-2 status, and patients' overall survival. Median Ki-67 expression in primary and metastatic tumors was 20% and 15%, respectively. Although there was no difference in overall survival (P = .65, log-rank test) between primary tumors with less than or at least 10% Ki-67 expression, there was significantly better overall survival when Ki-67 expression in lymph nodes was less than 10% (P = .040). For patients whose primary tumors exhibited Ki-67 expression less than 10%, most of their metastatic lesions had a similar low Ki-67; these patients had a favorable outcome. A small subgroup was noted to have a nodal Ki-67 of 10% or more and worse survival (P = .047). For patients whose primary tumors had a Ki-67 of 10% or more, most of their metastatic lesions had similar high Ki-67 values; however, a group of 12 patients had lymph node Ki-67 less than 10% and had a better overall survival (P = .092). Our results showed that measurement of Ki-67 in lymph node is superior to its evaluation in primary tumors. Identification of subgroups of patients in whom Ki-67 expression in lymph nodes differs from expression in primary tumor may assist in the selection of therapeutic options.