Endocrine Abstracts

Introduction

The diagnosis of insulinomas is made biochemically. However, proper localization of insulinomas is essential before surgery. Non-invasive methods including magnetic resonance imaging (MRI), computed tomography, ultrasonography, glucagon-like peptide-1 receptor PET/CT, 68Ga-DOTATATE PET/CT, and invasive methods such as endoscopic ultrasonography (EUS) and selective arterial calcium stimulation test are used for preoperative localization. However, some of these methods are either expensive and may not be available in most centers, or highly invasive that requires particular expertise. Therefore, we aimed to evaluate the role of EUS in the localization of insulinomas.

Case series

This case series including 8 patients with biochemically proven insulinomas. The age, gender, MRI, EUS, and immunuhistopathological results of the patients are shown in Table-1. A mass on MRI was detected in only 2 of the 8 patients. However, EUS showed a mass in the pancreas of all patients. All patients underwent surgery according to the EUS results, and a diagnosis of insulinoma was made in all patients by immunohistopathological analysis. All patients achieved cure after surgery except a patient with MEN-1 disease who had multiple small insulinomas as well as a glucagonoma.

Discussion

More than 90% of insulinomas are benign, solitary, and < 2 cm. However, MEN-1 associated insulinomas may be multiple. The sensitivity of CT and MRI is between 33% -64% and 40% -90%. However, no mass could be found by CT or MRI in 25–30% of the patients. In our series, the mass could not be detected in 6 of the 8 patients by MRI while all of the insulinomas were localized by EUS. On the other hand, the sensitivity of EUS decreases in the presence of a large number of tumors and small tumors, as in cases with MEN-1 disease. Therefore, EUS should be performed in all cases suspected of sporadic insulinomas before any other invasive localization method, but in patients with MEN-1 disease, other invasive and non-invasive localization methods should be performed even in the presence of a tumor on EUS.