Objective: The Ki-67 proliferation index has received an important role in treatment tailoring and molecular classification of estrogen receptor-positive breast carcinomas. The aim was to analyze the reproducibility of assessing proliferation on the basis of Ki-67 immunohistochemistry. Methods: Thirty core biopsy samples of breast cancer patients were analyzed after immunostaining with B56, SP6 and MIB-1 monoclonal Ki-67 antibodies. All samples were evaluated twice and independently by 3 pathologists, with each observer performing his daily routine practice. The ratio of Ki-67-positive cells was estimated with 5% accuracy. Correlation was calculated for the results of each investigator for all pairs of antibodies and for the results of each antibody for all pairs of investigators. Ki-67 scores were divided into categories of either 4 quarters or into 3 groups reflecting the St. Gallen consensus recommendations with 15 and 30% as cutoff values. The reproducibility of classifying the tumors into these categories was assessed with ĸ statistics. Results: Altogether, 540 evaluations were made. Good to excellent correlation (Spearman’s and Pearson’s coefficient range 0.74–0.92 and 0.73–0.93, respectively) was noted for the pairwise comparison of antibodies by observer and of observers by antibody. The inter- and intraobserver reproducibility of the Ki-67 score classification into equal quarters (1–25, 26–50, 51–75 and 76–100%) or into 3 categories with cutoffs at 15 and 30% was fair to poor in the middle categories, but moderate to substantial in the low and high ranges. Interobserver differences in practice potentially impacted on less consistent classification. Conclusion: Our results indicate that the three different Ki-67 antibodies tested do not substantially influence the reproducibility of the estimated proliferation rates. Although reproducibility is better in the clinically more relevant distinction of high versus low proliferation, without standardization, the current practice of Ki-67 assessment in many laboratories does not allow proper and consistent therapeutic decision-making.

The proportion of Ki-67 immunostained cells (Ki-67 labeling index, LI) is one of the most commonly used histology methods for estimating proliferation of breast carcinomas. Although the Ki-67 LI is used in treatment decision making, its reproducibility shows variation in different studies, and is generally less then optimal. The aim of the present study was to investigate how the use of a standardized, partially digitalized counting method could affect reproducibility of determining the Ki-67 LI. Thirty breast cancer core-biopsy samples were stained with B-56, SP-6 and MIB-1 monoclonal Ki-67 antibodies. Each sample was represented by a single digital photograph taken with a x20 objective. Four investigators determined the Ki-67 LI on these digital images by estimation, then by counting with the help of a grid overlaid on the same images. Altogether 720 evaluations were made by 4 independent pathologists. Good to excellent correlation was found between estimations and calculations of each observer. Kappa values >0.6 suggest substantial inter-observer agreement when classifying the cases into a 15 % and 30 % cut-off determined three-tiered or a 4-quarter-based four-tiered categorization, which is better than the fair reproducibility gained on the real slides in a previous study. The results also suggest that the type of the antibody may also impact on the consistency of both estimating and calculating the Ki-67 LIs. The results indicate that counting on digital images may significantly improve reproducibility of determining the KI-67 LI. Interestingly, estimation on the same images is not worse, but is obviously faster and more convenient.

Objectives: Individualized chemotherapy for breast cancer improves the outcome. Anthracyclines target the enzyme topoisomerase IIα (TOP2A). We set out to perform a retrospective study of the presence of gene abnormalities and the expression of TOP2A in a cohort of breast cancer patients treated with neoadjuvant anthracycline-based chemotherapy. Methods: Forty-three patients with 45 breast cancers were treated with neoadjuvant docetaxel-epirubicin with/without capecitabine chemotherapy. The TOP2A status of the cancers, determined retrospectively by fluorescent in situ hybridization and immunohistochemistry, was analyzed in relation to the standard clinical and pathological data. Results: Clinically and pathologically complete remission (pCR) was achieved in 15 (33.3%) and 9 (20%) cases, respectively. The TOP2A gene was amplified in 2 human epidermal growth factor receptor 2 (HER2)-positive cancers (8%), and 32 (84.2%) overall exhibited TOP2A expression in >15% of the cells. The expression of TOP2A exhibited a strong correlation with the expression of Ki67 (R = 0.743, p < 0.001), and was negatively correlated with estrogen receptors (ER; R = 0.404, p = 0.012) and progesterone receptors (R = 0.430, p = 0.007). The expression of TOP2A was not related to the amplification of the TOP2A gene or the HER2 status of the tumor. The proportions of Ki67- and TOP2A-positive tumor cells were significantly reduced after chemotherapy (56.1 ± 23.6 vs. 19.0 ± 27.7%, p = 0.004, and 41.0 ± 27.9 vs. 12.7 ± 24.8%, p < 0.001, respectively). The development of pCR was related to a high grade (p = 0.054), ER negativity (p = 0.027) and high TOP2A expression (p = 0.037). The expression of TOP2A was an independent predictor of pCR (OR = 1.460, for every 10% increase, 95% CI: 1.016–2.096, p = 0.041). After a median follow-up time of 31.0 months, neither relapse-free survival nor overall survival was related to the tumor response. Conclusions: TOP2A expression is a marker of the tumor’s proliferation rate and sensitivity to anthracycline-based chemotherapy, and does not depend on the amplification of its gene.

Introduction: Intraoperative touch imprint cytology (TIC) of the sentinel lymph node(s) (SLN(s)) in the treatment of breast cancer has significantly reduced the number of axillary block dissections (ABD) required during second surgeries. Based on recent studies, ABD was not considered necessary if the presence of tumor cells/micrometastasis was confirmed in the SLN(s) or in the case of macrometastases in a patient group meeting the inclusion criteria for the ACOSOG Z0011 study. Our aim was to determine the sensitivity and usefulness of TIC with regard to these results. Methods: TICs of the SLN(s) were examined in 1168 patients operated on for breast cancer. The method was also analyzed retrospectively based on the guidelines for the Z0011 study. During TIC, new samples were cut every 250 mm; impression smears were evaluated after being stained with hematoxylin eosin. Results: TIC confirmed metastasis in 202 cases (202/1168, 17.29%). Metastasis was confirmed in SLN(s) in 149 additional cases during a final histological examination. The sensitivity of TIC was found to be 57.18%, and its specificity was 99.63%. An analysis was then performed except for cases that met the inclusion criteria for the Z0011 study and with metastasis smaller than 2 mm (micrometastasis/isolated tumor cells) considered to be positive during intraoperative cytology. The sensitivity of the method decreased to 34.23%, while its specificity was still high at 99.76%. Conclusions: Based on the new guidelines for ABD, imprint cytology cannot be considered a beneficial and cost-effective intervention in the surgical treatment of early breast cancer.

The reproducibility of assessing potential biomarkers is crucial for their implementation. ONEST (Observers Needed to Evaluate Subjective Tests) has been recently introduced as a new additive evaluation method for the assessment of reliability, by demonstrating how the number of observers impact on interobserver agreement. Oestrogen receptor (ER), progesterone receptor (PR), and Ki67 proliferation marker immunohistochemical stainings were assessed on 50 core needle biopsy and 50 excision samples from breast cancers by 9 pathologists according to daily practice. ER and PR statuses based on the percentages of stained nuclei were the most consistently assessed parameters (intraclass correlation coefficients, ICC 0.918–0.996), whereas Ki67 with 5 different theoretical or St Gallen Consensus Conference–proposed cut-off values demonstrated moderate to good reproducibility (ICC: 0.625–0.760). ONEST highlighted that consistent tests like ER and PR assessment needed only 2 or 3 observers for optimal evaluation of reproducibility, and the width between plots of the best and worst overall percent agreement values for 100 randomly selected permutations of observers was narrow. In contrast, with less consistently evaluated tests of Ki67 categorization, ONEST suggested at least 5 observers required for more trustful assessment of reliability, and the bandwidth of the best and worst plots was wider (up to 34% difference between two observers). ONEST has additional value to traditional calculations of the interobserver agreement by not only highlighting the number of observers needed to trustfully evaluate reproducibility but also by highlighting the rate of agreement with an increasing number of observers and disagreement between the better and worse ratings.