Pancreatic Well-Differentiated Neuroendocrine Tumors are Frequently Undergraded on Endoscopic Ultrasound-Guided Fine Needle Biopsy Sampling: A Single Institutional Experience.

Objectives. To determine the accuracy of grading pancreatic well-differentiated neuroendocrine tumors (PanNETs) on endoscopic ultrasound-guided fine needle biopsy (EUS-FNB). Methods. Fifty-three (53) PanNETs from 52 patients with EUS-FNB and subsequent resection were included, including 1 patient with 2 synchronous tumors biopsied separately. Grade (G) was assigned as per the 2019 World Health Organization criteria. The concordance of grade between EUS-FNB and resection was measured using kappa statistic. Clinicopathologic features were compared between specimens with concordant or discordant grading. Results. Two-thirds of patients were male, and the median age was 62 years (range 27-85). Four received neoadjuvant therapy. 89% were nonfunctional, whereas 11% were functional. Concordance of grade between EUS-FNB and resection was moderate (kappa = 0.45). Precisely 25% (13 out of 51) of G1 or G2 specimens were discordant. G2 tumors were frequently undergraded on EUS-FNB (11 out of 18; 61%), whereas G1 tumors were only rarely overgraded (2 out of 33; 6%). Two G3 tumors were concordant. There was no correlation between concordance and other clinicopathologic features, except for perineural invasion. Conclusions. The concordance of PanNET grading between EUS-FNB and resection was moderate, and G2 tumors were frequently undergraded on EUS-FNB. Knowledge of this is important to recognize and acknowledge, as this could potentially impact treatment decisions in some patients.