The role of Ki-67 in the proliferation and prognosis of breast cancer molecular classification subtypes

The Ki-67 antigen was identified in the early steps of polymerase I-dependent ribosomal RNA synthesis. Although it seems that this protein has an important function in cell division, its exact role is still unclear and there is little published work on its overall function. The aim of the present study was to evaluate the contribution of the level of Ki-67 with respect to tumor recurrence in molecularly classified groups of breast cancer patients. Ki-67 was divided into the percentage levels up to and including 20% and over 20%. Immunohistochemistry and fluorescence in-situ hybridization are described for the results of estrogen receptor, progesterone receptor, c-erb-B2, and Ki-67 biomarkers. Formaldehyde-fixed breast samples were paraffin wax embedded and processed for paraffin sections. The protocol of the present study started in 1995 and finished in 2010. Nine hundred and sixteen patients with breast cancer were examined: 291 were grouped as luminal A, 228 as luminal B, 221 as the Her-2 subtype, and 107 as basal cell (triple negative). Follow-up ranged from 3 to 15 years following diagnosis. It was found that in luminal A patients, only one had a Ki-67 level higher than 20%. In luminal B, the Ki-67 was higher than 20% in 51.16% of the patients and recurrence occurred in 23.68%. In the Her-2 subtype, the Ki-67 level was more than 20% in 48.63%. In basal cell triple-negative patients, Ki-67 was more than 20% in 63.86%. The data presented here indicate that the level of Ki-67 may be considered one of the valuable biomarkers in breast cancer patients with respect to process and recurrence.