Endoscopic ultrasound-guided fine-needle aspiration for the diagnosis and grading of pancreatic neuroendocrine tumors: a retrospective analysis of 110 cases

Background Data on the reliability of the Ki-67 index and grading calculations from endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) of pancreatic neuroendocrine tumors (PanNETs) are controversial. We aimed to assess the accuracy of these data compared with histology. Methods Cytological analysis from EUS-FNA in patients with suspected PanNETs (n = 110) were compared with resection samples at a single institution. A minimum of 2000 cells were considered to be adequate for grading. Correlation and agreement between cytology and histology in grading and Ki-67 values, respectively, were investigated. Secondary outcomes included the diagnostic performance of EUS-FNA. Results EUS-FNA samples were adequate for PanNET diagnosis and PanNET grading in 98/110 (89.1%) and 77/110 (70.0%) patients, respectively; thus, 77 samples were adequate for comparing cytology vs. histology. There were 67 (62.0%), 40 (36.4%), and 1 (0.9%) patients with a final diagnosis of G1, G2, and G3 tumors, respectively. EUS-FNA grading was concordant with surgical pathology in 81.8% of patients; under-and overgrading occurred in 15.6% and 2.6%, respectively. The overall level of agreement for grading was moderate (Cohen's. = 0.59, 95% confidence interval [CI] 0.34-0.78). Spearman's rho for Ki-67 in tumors >= 20mm and > 20mm was strong and moderate, respectively (rho = 0.68, 95 %CI 0.47-0.83; rho = 0.59, 95% CI 0.35-0.75). The Bland-Altman plot showed that the Ki-67 values were comparable and reproducible between the two measurements. Conclusions Although they were not available for a significant number of patients, grading and Ki-67 values from cytology correlated with histology moderately to strongly.