Endoscopic ultrasonography of nonfunctioning pancreatic islet cell tumors with histologic correlation

Background/Aims: Preoperative differentiation of benign and malignant pancreatic nonfunctioning islet cell tumors remains problematic. The present study aimed to evaluate endoscopic ultrasonography (EUS) features of benign and malignant tumors with histologic correlation. Methodology: Ten patients with surgically resected nonfunctioning pancreatic islet cell tumors were retrospectively reviewed. Results: EUS demonstrated a homogenous hypoechoic (n = 2) or hyperechoic (n = 1) mass in the 3 benign tumors. EUS showed a hypoechoic mass with an irregular central hyperechoic portion (n = 4), a hyperechoic mass with an irregular central hypoechoic portion (n = 1), a cystic mass with a large irregular internal hypoechoic portion (n = 1), or a hypoechoic mass within the entire lumen of the main pancreatic duct (MPD) (n = 1) in the 7 malignant tumors. Histologically, the irregular central portions of the malignant tumors corresponded to necrosis, hemorrhage, fibrosis with hyalinosis, cystic degeneration, and/or calcification. Complete obstruction of the main pancreatic duct on EUS was observed in the 2 malignant tumors. The echogenicity of the tumors was closely associated with arrangement of tumor cells and quantity of fibrous stroma. Conclusions: Heterogeneous internal structures and complete obstruction of the main pancreatic duct are considered as important EUS features that are suggestive of malignancy in nonfunctioning pancreatic islet cell tumors.