Fine-needle aspiration biopsy of pancreatic neuroendocrine tumors: Correlation between Ki-67 index in cytological samples and clinical behavior

BackgroundMitotic count in hematoxylin-eosin stained slides and Ki-67 index allow stratification of patients for prognosis and therapeutic decision making in pancreatic neuroendocrine tumors (PNETs). However, the utility of Ki-67 determination in cytological material and its association to PNET prognosis are under discussion. MethodsWe have retrospectively reviewed all cases of EUS-FNA cytology of pancreatic lesions performed in the Hospital Clinico San Carlos (Madrid) between 2006 and 2016. We have analyzed the potential association between the Ki-67 estimation in PNET cytological material and patient outcomes. ResultsWe identified 24 PNET cases. Mean age was 56.8 years and most patients were males (54%). PNETs were mainly located in the head and tail of the pancreas and the mean tumor size was 36 mm. Cell block from cytology was available in 12 cases (50%), and there were 19 G1, 2 G2, and 3 G3 tumors. All cases graded as G2 (2 patients) or G3 (three patients) on cytology were stage IV, and the 19 cases graded as G1 ranged from stages IA to IV. All patients with G2 tumors on cytology died due to PNET. Of the three patients with G3 lesions, two died of disease and the other died 2 months after diagnosis from causes other than PNET. 78% of the patients with G1 tumors are stable and currently being followed-up. ConclusionHigher Ki-67 index in cytology specimens portends a worse outcome, although some G1 tumors may progress or cause death. Diagn. Cytopathol. 2017;45:29-35. (c) 2016 Wiley Periodicals, Inc.