Pancreatic neuroendocrine tumour grading on endoscopic ultrasound-guided fine needle aspiration: high reproducibility and inter-observer agreement of the Ki-67 labelling index.

Objectives Assessment of proliferation by the Ki-67 labelling index ( Ki67- LI) is an important parameter of pancreatic neuroendocrine tumour ( pNET) prognosis on resection specimens. Ki67- LI values for grading are not fully established on endoscopic ultrasound-guided fine needle aspiration ( EUS- FNA). The aim of the study was to determine the accuracy of Ki67- LI on EUS- FNA to predict a final grade of p NET and to analyse the relationship between cytological grading and progression-free survival ( PFS). Methods Between 1996 and 2010, 46 pNETs (33 were resected) from 45 patients were diagnosed by EUS- FNA. Ki67-LI was evaluated on cytological and histological material for each tumour and classified according to the 2010 WHO grading system. Results A very good inter-observer agreement for Ki67- LI on EUS- FNA and surgical specimens, respectively, were obtained. Discrepancies were observed between histology and cytology, especially in grade 2 ( G2) tumours, where cytology underestimated grading owing to tumour heterogeneity. Still, EUS- FNA was able to distinguish a poor prognostic group, as the actuarial PFS of cytological (c) G3 tumours was 10 ± 4 months versus 29 ± 7 and 68 ± 10 for c G2 and c G1 tumours, respectively ( P < 0.0001). Conclusion This study attests the reproducibility of Ki67- LI of pNETs whether counted on cytology or histology with a very good inter-observer correlation. Determination of Ki67- LI on EUS- FNA of pNETs should be included systematically in their prognostic work-up. [ABSTRACT FROM AUTHOR]