Reliability of Proliferation Assessment by Ki-67 Expression in Neuroendocrine Neoplasms: Eyeballing or Image Analysis?

Abstract

Background: The latest WHO classification for neuroendocrine neoplasms (NEN) of the gastrointestinal tract defines grade according to Ki-67 and mitotic indices. Some have questioned the reproducibility and thus the reliability of Ki-67 assessment. We therefore investigated the accuracy of this proliferation marker in NEN. Methods: The Ki-67 index of tumor specimens of NEN (n = 73) was assessed by two pathologists as in routine practice with eyeballing and twice by image analysis using ImageJ freeware at different magnifications. Results were correlated with overall survival. Results: The intraclass correlation coefficient (ICC) between pathologists was 0.88. The ICC for the measurements using image analysis was 0.85. The ICC between all four measurements (pathologists and ImageJ) was 0.80. If the Ki-67 index was translated to grade as prescribed by the current WHO classification (<3% = grade 1, 3-20% = grade 2, >20% = grade 3), kappa was between 0.61 and 0.75. Grades based on pathologist scoring were often (16-29%) higher than grades assigned by image analysis (p < 0.001). Grade was significantly correlated with survival (p < 0.0001) irrespective of the way Ki-67 was assessed. Conclusion: Assessment of the Ki-67 index by eyeballing correlates remarkably well with the Ki-67 index as calculated by image analysis and is therefore an accurate parameter. Moreover, it is significantly related to survival irrespective of the method used. Yet if the Ki-67 index is translated to grade, the grade should be interpreted with caution due to values around threshold levels.

Comparative evaluation of three proliferation markers, Ki-67, TOP2A, and RacGAP1, in bronchopulmonary neuroendocrine neoplasms: Issues and prospects

“…Here, between the tumor entities, a similar constellation was found as in both manual counting methods. The data are in accordance with many other studies comparing automated digital image analysis with the manual methods, but in some investigations also higher or equal limits were observed [31, 33, 36–38]. The discrepancies between published results may result from differences in the programs used for digital image analysis.…”

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

“…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].…”

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

“…More recently, it has become clear that tumor grade based on Ki67 proliferative index is a better measure of tumor behavior than mitotic count. (2-4) Thus, accurate assessment of Ki67 proliferative index is essential for determination of tumor grade. This information, in turn, is essential for accurate prognostication and optimal patient management.…”