295 Validation of a Cytotechnologist Manual Counting Service for the Ki67 Index in Neuroendocrine Tumors of the Pancreas and Gastrointestinal Tract

Abstract

Pathologists routinely assess Ki67 immunohistochemistry to grade gastrointestinal and pancreatic neuroendocrine tumors. Unfortunately, manual counts of the Ki67 index are very time consuming, and “eyeball estimation” has been criticized for being unreliable. Manual Ki67 counts performed by cytotechnologists could potentially save pathologist time and improve accuracy. To assess the concordance between manual Ki67 index counts performed by cytotechnologists vs eyeball estimates and manual Ki67 counts by pathologists. Ki67 immunohistochemical stains were retrieved from archived gastrointestinal or pancreatic neuroendocrine tumor resections. We compared pathologist Ki67 eyeball estimates on glass slides and printed color images with manual counts by three cytotechnologists and gold standard manual Ki67 index counts by three pathologists. Tumor grade agreement between pathologist image eyeball estimate and gold standard pathologist manual count was fair (K value of 0.31 [95% CI 0.03–0.60]). In nine of 20 cases (45%), the mean pathologist eyeball estimate was one grade higher than the mean pathologist manual count. There was almost perfect agreement in classifying tumor grade between the mean cytotechnologist manual count and the mean pathologist manual count (K value of 0.91 [95% CI 0.7–1.0]). In 20 cases, there was only one grade disagreement between the two methods. Eyeball estimation by pathologists required less than one minute, while manual counts by pathologists required a mean of 17 minutes per case. Eyeball estimation of the Ki67 index has a high rate of tumor grade misclassification compared to manual counting. Cytotechnologist manual counts are accurate and save pathologists time.