Immunohistochemical analysis of proliferation markers such as Ki-67 and
cyclin A is widely used in clinical evaluation as a prognostic factor in
breast cancer. The proliferation status of
tumors is guiding the decision of whether or not a patient should be treated with
chemotherapy because low-proliferative
tumors are less sensitive by such treatment. However, the lack of optimal cutoff points and selection of
tumor areas hamper its use in clinical practice. This study was performed to compare the Ki-67 and
cyclin A expression counted in hot-spot vs average counting based on 5 to 14 random
tumor areas in 613
breast carcinomas. We correlated the findings with 10-year follow-up in order to standardize the evaluation of proliferation markers in clinical practice. A significant correlation was found between the percentage of positive cells estimated by Ki-67 and
cyclin A both by hot-spot and by average counting. Both methods showed that high expression of Ki-67 and
cyclin A is associated with more adverse
tumor stage. The cutoff value for Ki-67 for distant
metastases was set to 22% and to 15%, using hot-spot and average counting, respectively. For
cyclin A, the values were set to 14% and 8% using the respective methods. Survival curves revealed that patients with a high hot-spot proliferation index had a significantly greater risk of shorter
tumor-free survival. Our findings suggest that the determination of proliferation markers in
breast cancer should be standardized to hot-spot counting and that specific cutoff values for proliferation could be useful as prognostic markers in clinical practice. Moreover, we suggest that expression levels of
cyclin A could be used as a complementary marker to estimate the proliferation status in
tumors, especially those with "borderline" expression levels of Ki-67, in order to more accurately estimate the proliferations status of the
tumors.