Diagnosis value preoperative localization of insulinoma by diffusion-weighted imaging: A pilot study

Insulinoma is the most common functional neuroendocrine tumor that originates from the islet of beta cells. Insulinoma is usually an isolated benign tumor and small in size (<2 cm). Due to the small size of the lesion, it often leads to difficulty in clinical preoperative localization diagnosis. However, we have unexpectedly discovered that the diffusion-weighted-imaging (DWI) adds great value in the preoperative localization diagnosis of insulinoma in non-invasive examination technique.We verified using operative pathology data and retrospectively analyzed the clinical and imageology findings of 5 cases who reported to have an insulinoma. All the 5 cases underwent DWI examination, among non-contrast enhanced magnetic resonance imaging (MRI) in 1 case, contrast-enhanced MRI in 4 cases.Five cases of DWI showed a nodular high signal <1.3 cm with pancreatic tail in 3 cases, pancreatic neck, and pancreatic head in 1 case each, respectively. Non-contrast enhanced MRI showed suspicious abnormal signals in the tail of the pancreas were detected in 1 case. MRI enhanced scans presented 2 cases with abnormal enhancement in the arterial phase and 2 cases without abnormal enhancement in arterial phase. Also, 3 cases showed mild persistence enhanced in the portal venous phase and delayed phase. However, 1 case remained normal in the portal venous phase and the delay period.DWI examination has high clinical value in the localization diagnosis of insulinoma and thus it can be used as a routine examination for preoperative localization diagnosis.