Endoscopic ultrasound-guided side-fenestrated needle biopsy sampling is sensitive for pancreatic neuroendocrine tumors but inadequate for tumor grading: a prospective study

Accurate pretreatment grading of pancreatic neuroendocrine tumors (PanNETs) is important to guide patient management. We aimed to evaluate endoscopic ultrasound-guided fine needle biopsy sampling (EUS-FNB) for the preoperative diagnosis and grading of PanNETs. In a tertiary-center setting, patients with suspected PanNETs were prospectively subjected to 22-gauge, reverse-bevel EUS-FNB. The EUS-FNB samples (Ki-67(EUS)) and corresponding surgical specimens (Ki-67(SURG)) were analyzed with Ki-67 indexing and thereafter tumor grading, (GRADE(EUS)) and (GRADE(SURG)) respectively. In total 52 PanNET-patients [median age: 66 years; females: 25/52; surgical resection 22/52 (42%)] were included. EUS-FNB was diagnostic in 44/52 (85%). In 42 available FNB-slides, the median neoplastic cell count was 1034 (IQR: 504-3667) with 32/42 (76%), 22/42 (52%), and 14/42 (33%) cases exceeding 500, 1000, and 2000 neoplastic cells respectively. Ki-67(SURG) was significantly higher compared to Ki-67(EUS) with a moderate correlation comparing Ki-67(EUS) and Ki-67(SURG) (Pearson r = 0.60, r(2) = 0.36, p = 0.011). The GRADE(EUS) had a weak level of agreement (kappa = 0.08) compared with GRADE(SURG). Only 2/12 (17%) G2-tumors were correctly graded in EUS-FNB-samples. EUS-guided fine needle biopsy sampling is sensitive for preoperative diagnosis of PanNET but biopsy quality is relatively poor. Therefore, the approach seems suboptimal for pretreatment grading of PanNET.

Automated summary

This study aimed to evaluate the use of endoscopic ultrasound-guided fine needle biopsy sampling (EUS-FNB) for the preoperative diagnosis and grading of pancreatic neuroendocrine tumors (PanNETs). The results showed that EUS-FNB had high sensitivity for preoperative diagnosis of PanNETs, but the quality of the biopsy samples was relatively poor, making it suboptimal for preoperative grading.