Background: Incidentally discovered, nonfunctioning pancreatic endocrine tumors (NF-pNETs) are being increasingly diagnosed with the widespread use of imaging examination. The objective of this study was to analyze the different clinicopathologic and imaging features between incidentally discovered and symptomatic NF-pNETs.

Methods: From March 2010 to October 2014, we retrospectively analyzed 102 patients with pathologically confirmed sporadic NF-pNETs, among which 49 (48.0%) had lesions that were discovered incidentally. Differences in clinicopathologic features and various computerized tomography (CT) and endoscopic ultrasonography (EUS) findings were evaluated between incidental and symptomatic NF-pNETs.

Results: Among 102 patients with NF-pNETs, 49 (48.0%) had lesions that were discovered incidentally. Incidental NF-pNETs were more highly associated with low tumor grades, stages and lymphatic metastasis compared with symptomatic tumors (p = 0.007, 0.029 and 0.003, respectively). Moreover, incidental NF-pNETs had a lower rate of hypoenhancement (p = 0.018), main pancreatic duct dilatation (p = 0.043), and unclear border (p = 0.022). In addition, hypoechoic lesion was the most common and had a slightly higher rate in symptomatic tumors (p = 0.032).

Conclusions: Incidental NF-pNETs are associated with lower rates of aggressive behaviors of clinicopathologic and imaging features compared with symptomatic tumors.