Abstract
Introduction/Objective
Proliferative activity is an essential prognostic and treatment indicator for neuroendocrine tumors (NET). Ki-67 proliferation index, if reported by unaided microscopic estimation on hot-spot locations could lead to variability and inconsistencies. This study aims to compare the Ki-67 assessment of NETs by visual estimation versus automated digital image analysis (Roche iCoreo/Virtuoso).
Methods
212 patients with Ki-67-graded GI NETs (117 G1; 61 G2; 34 G3) from 2010 to 2019 were reassessed using digital image analysis quantification of hot spot areas of at least 500 cells (average 800 cells). Revised tumor grades were assigned according to the European Neuroendocrine Tumor Society guidelines and the 2010 World Health Organization classification and compared to initially reported grade.
Results
We found 75% concordance for G1, with 22% of cases upgraded to G2 and 3% of cases upgraded to G3. For G2, there was 70.5% agreement, with 13.1% of cases downgraded to G1 and 16.4% upgraded to G3. For G3, there was 100% agreement, (kappa=0.64, overall). Retrospective review of discordant G3 cases revealed cases with known metastasis, small fragments of tissue, or polyps. Scanning and scoring required approximately 10 minutes per case.
Conclusion
Our data shows the time/effort difference of visually estimating versus automated digital analysis may lead to significant classification errors in these tumors. Although digital analysis has limitations, including tumor heterogeneity, misidentification of tumor cells, and poor immunostaining which could require manual counting by a pathologist, this rigor should be reinforced and explicitly stated to increase accuracy and reproducibility of grading.