Endoscopic ultrasound-guided fine needle aspiration of pancreatic neuroendocrine tumours with rapid on-site evaluation: single center experience.

Introduction: Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) is a highly sensitive and accurate method for identifying pancreatic neuroendocrine tumors (PanNETs). However, research on grading and assessing the Ki67 proliferation index in FNA samples is limited.

Methods: This study analyzed 335 EUS-FNA cases performed between 2016 and 2022, of which 12 cases of PanNET were further evaluated. The morphology, Ki-67 index, and grading (G) of cell blocks (CB) obtained from the PanNET aspirations were compared to those of the resected material.

Results: Out of 12 PanNET's with rapid on-site evaluation(ROSE), in FNA samples and CB,7 (58.3%) cases were G1,while 5 (41.7%) cases were G2.On the other hand,resection of these cases,6 (50%) were diagnosed as G1,5(41.7%) cases were G2,and 1 case(8.3%) was G3.The average ki67 index in CB was 2.92(min: 1-max: 10), while in resections it was 4.67(min: 1-max: 22).Only 2(16.6%) showed a discordance between grade and ki67, resulting in an overall concordance of over 80%.On average,1.83 needle passes were made(range: 1-3), while the average number of slides and cell blocks were 9.33(range: 1-24) and 2.17(range: 1-6),respectively.There were no significant differences in the number of passes,slides,or cell blocks between the consistent and discordant groups.

Conclusion: Optimal counting techniques and sensitivity for Ki67 are crucial in grading PanNETs in both aspiration and resection materials.The grade and Ki67 index demonstrated high concordance when comparing CB and resection. However, in low-volume centers, ROSE support can be beneficial in obtaining sufficient slides and cell blocks for an adequate diagnosis.