Comparison of Three Ki-67 Index Quantification Methods and Clinical Significance in Pancreatic Neuroendocrine Tumors

Abstract

The Ki-67 index is essential in the pathological reports for pancreatic neuroendocrine tumors. There are three methods to determine the Ki-67 index including eyeball estimation, manual counting, or automated digital imaging analysis. The goal of this study was to compare the three quantification methods with the clinical outcome to determine the best method for clinical practice. Ki-67 immunostaining was performed on 97 resected pancreatic neuroendocrine tumors. The three methods of quantification were employed: (1) an average of eyeball estimation by three pathologists; (2) manual counting of at least 500 tumor cells; and (3) digital imaging analysis quantitation by selecting 8-10 hot spot regions. All tumors were graded according to the 2010 WHO grading system. The three quantification methods for the Ki-67 index had almost perfect agreement. The concordance between manual counting and digital imaging analysis and between manual counting and average eyeball estimation were 0.97 and 0.88, respectively. The concordance among the three pathologists' eyeball estimation was 0.86. All three methods correlated with patients' survival using the 2010 WHO grading system. Eyeball estimation scores were significantly less than those of the other two methods and tended to downgrade more tumors to grade 1, but they had higher predictive ability for survival and recurrence. The WHO system using the mitotic rate could also separate patients with different survival and even downgraded more tumors to grade 1. The results suggest the necessity of a consensus among pathologists for the method to determine the Ki-67 index and proper cutoff of the Ki-67 index for better clinical correlation.

Tissue heterogeneity contributes to suboptimal precision of WHO 2010 scoring criteria for Ki67 labeling index in a subset of neuroendocrine neoplasms of the pancreascriteria for Ki67 labeling index in a subset of neuroendocrine neoplasms of the pancreas

“…However, multi-institutional studies showed that formal counting was more reproducible than estimation in breast cancer [53,75]. Similar observation were made in NEN: results of eyeballed estimation differed from results of counting [20,21,25] and were irreproducible [25], but some investigators showed that estimation was not as bad [27,28]. Pathologists in general overestimate the Ki67 LI during eye-balled estimation in comparison to counting technique [25,27].…”

“…Analytical validity is a sine qua non condition for any tumour biomarker which is intended to be used in clinical practice and to influence management of the patients [18]. Selected aspects of analytical validity of Ki67 LI in NEN were previously studied [19,20,21,22,23,24,25,26,27,28].…”

Cut‐point for Ki‐67 proliferation index as a prognostic marker for glioblastoma

“…These measures likely minimized the impact of inter‐ and intraobserver variability in Ki‐67staining quantification. In addition, the most reliable, albeit time‐consuming manual counting technique for Ki‐67 was used in this study . These above points are major strengths of our study.…”

Synaptophysin-Ki67 double stain: a novel technique that improves interobserver agreement in the grading of well-differentiated gastrointestinal neuroendocrine tumors

“…Emphasizing the importance of this, Adsay noted, “In our experience, almost half of the cases are placed in a different World Health Organization grade on the basis of the area chosen for counting.” (22) In our study, interobserver agreement for Ki67-only stained slides was similar to that seen by Reid et al (21) using their “manual eye count” – a method equivalent to that used in the current study. It is also worthwhile noting that a subset of studies focuses solely on pancreatic neuroendocrine tumors (8, 21, 26) – which are morphologically more homogeneous with few peri-tumoral stromal lymphocytes or entrapped non-neoplastic glands. Thus, these studies may not capture the intricacies related to assessing Ki67 proliferative index of gastrointestinal neuroendocrine tumors in general.…”