Ki‐67 labeling: A more sensitive indicator of malignant phenotype than mitotic count or tumor size?

BACKGROUND AND OBJECTIVES: The Ki-67 index has been incorporated into The World Health Organization's classification system of pancreatic neuroendocrine tumors. However, pathologists continue to question the utility of Ki-67 index over that of mitotic count as an indicator of proliferative activity. The intent of the current study is to compare K-i67 index with tumor size and mitotic rate for the association of each with lymph node metastasis and survival. METHODS: The current study is a review of 24 patients with pancreatic neuroendocrine tumors. RESULTS: Regional LNM were present in 100% of tumors with Ki-67 index >10%, while only 25% of tumors with <10% Ki-67 had LNM (P = 0.003). No tumors <2 cm had >10% Ki-67 labeling. Of patients with tumors showing ≥ 10% Ki-67 labeling, 80% died during the observation period of this study, while during the same time period, no patients with <10% Ki-67 labeling died. CONCLUSION: Ki-67 index of >10% is a sensitive indicator of malignant behavior and mortality. Future advances in management of pNETs will require development of staging guidelines with higher predictive value. Inclusion of Ki-67 labeling >10% as an indicator of aggressive disease may contribute to such improvements.