Should the Selective Arterial Secretagogue Injection Test for Insulinoma Localization Be Evaluated at 60 or 120 Seconds?

Intraoperative selective arterial calcium injection test to confirm complete resection of a proinsulinoma

Proinsulinoma is a subtype of insulinoma that is surgically curable, but localization can be difficult as these tumors are typically too small to be visualized by imaging. We report the case of a 53-year-old woman referred to our hospital with dizziness and headache. Her blood glucose level was 46 mg/dl and Whipple's triad was present. Although her immunoreactive insulin level during hypoglycemia was in the normal range (5.0 μU/ml), the proinsulin level was elevated (408 pmol/l). Imaging examinations showed no evidence of pancreatic tumor. A preoperative selective arterial calcium injection (SACI) test showed excessive insulin secretion in the splenic artery region, which localized the proinsulinoma to the body or tail of the pancreas, and laparoscopic spleen-preserving distal pancreatectomy was performed. Intraoperative SACI test performed after tumor removal did not show excessive insulin secretion. The intraoperative SACI test appears to be useful for localization and for confirming complete resection of proinsulinoma.

Low-dose Selective Arterial Calcium Stimulation Test for Localizing Insulinoma: A Single-center Experience of Five Consecutive Cases

The selective arterial calcium stimulation test (SACST) is one of the most useful localization tests for insulinoma but can cause false-positive and/or unexpected multi arterial positive results that hamper clinical decisions. There are also several adverse effects, such as nausea and hypoglycemia, at the conventional dose (0.025 mEq/kg) of calcium injection. We herein report five consecutive insulinoma cases in which low-dose (0.005-0.007 mEq/kg) calcium injection for SACST led to successful insulinoma localization. No adverse effects of SACST were observed. In conclusion, a low-dose SACST can be a favorable option as an insulinoma localization test in terms of accuracy and safety.

Diagnostic accuracy of selective arterial calcium injection test for localization of gastrinoma

The appropriate localization of gastrinoma is still difficult. We aimed to evaluate the diagnostic accuracy of selective arterial calcium injection (SACI) for localization of gastrinomas including multiple lesions. This retrospective study included ten patients with surgically proven gastrinomas (gastrinoma group) and six patients without any findings suggesting Zollinger-Ellison syndrome (non-gastrinoma group). For SACI, calcium gluconate was injected into the arteries supplying pancreas, duodenum, and liver. Blood samples from the hepatic vein were obtained before and 30, 60, and 120 seconds after each injection. The results were considered positive when the increase in serum immunoreactive gastrin (IRG) levels within 60 seconds of calcium gluconate injection were more than 80 pg/mL and more than 20% from baseline. We evaluated the efficacy of SACI by comparing the SACI responses with definitive locations diagnosed by clinical and histopathological findings. In the gastrinoma group, false-positive responses were confirmed in seven of the ten patients. False-negative response was observed in one of the feeding arteries of one patient with gastrinomas in multiple locations. Conversely, the greatest increase in serum gastrin levels from baseline at 30 seconds indicated the true-positive responses in all patients with gastrinomas. In the non-gastrinoma group, calcium gluconate injection into gastroduodenal artery evoked positive responses in five of the six patients. In conclusion, our data suggest the strongest gastrin response evoked by SACI indicates the definitive location in patients with gastrinomas. In contrast, SACI could not accurately locate multiple gastrin-secreting lesions due to poor specificity.

Surgical Management, Preoperative Tumor Localization, and Histopathology of 80 Patients Operated on for Insulinoma

INTRODUCTION

Diagnosis and pathological classification of insulinomas are challenging.

AIM

To characterize localization of tumors, surgery outcomes, and histopathology in patients with insulinoma.

METHODS

Patients with surgically resected sporadic insulinoma were included.

RESULTS

Eighty patients were included. Seven had a malignant tumor. A total of 312 diagnostic examinations were performed: endoscopic ultrasonography (EUS; n = 59; sensitivity, 70%), MRI (n = 33; sensitivity, 58%), CT (n = 55; sensitivity, 47%), transabdominal ultrasonography (US; n = 45; sensitivity, 40%), somatostatin receptor imaging (n = 17; sensitivity, 29%), 18F-fluorodeoxyglucose positron emission tomography/CT (n = 1; negative), percutaneous transhepatic venous sampling (n = 10; sensitivity, 90%), arterial stimulation venous sampling (n = 20; sensitivity, 65%), and intraoperative US (n = 72; sensitivity, 89%). Fourteen tumors could not be visualized. Invasive methods were used in 7 of these 14 patients and localized the tumor in all cases. Median tumor size was 15 mm (range, 7 to 80 mm). Tumors with malignant vs benign behavior showed less staining for insulin (3 of 7 vs 66 of 73; P = 0.015) and for proinsulin (3 of 6 vs 58 of 59; P < 0.001). Staining for glucagon was seen in 2 of 6 malignant tumors and in no benign tumors (P < 0.001). Forty-three insulinomas stained negative for somatostatin receptor subtype 2a.

CONCLUSION

Localization of insulinomas requires many different diagnostic procedures. Most tumors can be localized by conventional imaging, including EUS. For nonvisible tumors, invasive methods may be a useful diagnostic tool. Malignant tumors showed reduced staining for insulin and proinsulin and increased staining for glucagon.

Imaging of pancreatic neuroendocrine tumors: recent advances, current status, and controversies

INTRODUCTION

Recently, there have been a number of advances in imaging pancreatic neuroendocrine tumors (panNETs), as well as other neuroendocrine tumors (NETs), which have had a profound effect on the management and treatment of these patients, but in some cases are also associated with controversies. Areas covered: These advances are the result of numerous studies attempting to better define the roles of both cross-sectional imaging, endoscopic ultrasound, with or without fine-needle aspiration, and molecular imaging in both sporadic and inherited panNET syndromes; the increased attempt to develop imaging parameters that correlate with tumor classification or have prognostic value; the rapidly increasing use of molecular imaging in these tumors and the attempt to develop imaging parameters that correlate with treatment/outcome results. Each of these areas and the associated controversies are reviewed. Expert commentary: There have been numerous advances in all aspects of the imaging of panNETs, as well as other NETs, in the last few years. The advances are leading to expanded roles of imaging in the management of these patients and the results being seen in panNETs/GI-NETs with these newer techniques are already being used in more common tumors.