Imaging and localization of islet-cell tumours of the pancreas on CT and MRI

A Five-Year Journey to Diagnosis: Resolving Persistent Hypoglycemia Through Successful Insulinoma Resection-A Case Report

Insulinoma is a rare functional pancreatic neuroendocrine tumor with an annual prevalence of 0.5-5 cases per million. It is characterized by excessive insulin secretion, leading to recurrent hypoglycemia, often diagnosed through Whipple's triad: hypoglycemic symptoms, documented low plasma glucose, and symptom resolution after glucose administration. Approximately 90% of insulinomas are sporadic, while 10% are associated with multiple endocrine neoplasia type 1. Diagnosis is frequently delayed due to nonspecific symptoms and misattributions to neurological or psychiatric conditions. Biochemical confirmation through a supervised fasting test and advanced imaging modalities, including CT, MRI, and endoscopic ultrasound (EUS), is essential for identifying and localizing the tumor. We report the case of a 52-year-old male who presented with a 5-year history of recurrent fasting and postprandial hypoglycemic episodes, including adrenergic and neuroglycopenic symptoms such as palpitations, diaphoresis, dizziness, and episodes of altered sensorium. Initial evaluations misattributed his symptoms to neurological and cardiac disorders, delaying diagnosis. Upon presentation, Whipple's triad was confirmed, and biochemical testing revealed hyperinsulinemic hypoglycemia (plasma glucose: 27 mg/dL, serum insulin: 45.83 mIU/L, C-peptide: 7.03 ng/mL). Imaging identified a 3 × 3 cm hypervascular lesion in the pancreatic tail. The patient underwent distal pancreatectomy, and histopathological analysis confirmed a grade 1 neuroendocrine tumor. Postoperative outcomes were favorable, with complete resolution of symptoms and normalization of glucose and insulin levels. Follow-up showed no recurrence of hypoglycemia. This case underscores the challenges in diagnosing insulinoma due to nonspecific symptoms and highlights the importance of Whipple's triad, biochemical tests, and imaging in timely diagnosis. Surgical resection remains the definitive treatment, with excellent long-term outcomes when performed promptly.

Pancreatic Neuroendocrine Tumors-Diagnostic Pitfalls of Non-Diabetic Severe Hypoglycemia: Literature Review and Case Report

Background: Hypoglycemia in the case of persons without diabetes is a rare event, being usually, initially misinterpreted based on the symptoms that can mimic various diseases, especially of a neuro-psychiatric nature. In the case of the identification of insulin-mediated hypoglycemia, the evaluation of pancreatic neuroendocrine tumors, which represent the most common and worrisome causes of non-diabetic insulin-mediated hypoglycemia, must be considered. Case Report: We present the case of a 57-year-old patient, hospitalized for a history of approximately one month of recurrent episodes of symptoms suggestive for severe hypoglycemia. The biological evaluation performed during an episode of hypoglycemia showed a plasma glucose value of 44 mg/dL, insulinemia 16.3 µU/mL, C peptide 3.72 ng/mL, HbA1c 4.99%, absence of urinary ketone bodies and anti-insulin antibodies <0.03 U/mL. The CT and MRI examination showed a 15.3/15 mm rounded tumor in the pancreatic corporeo-caudal region. The pancreatic tumor formation was enucleated and the histopathological and immunohistochemical analysis confirmed the diagnosis of the pancreatic neuroendocrine tumor with a positive reaction for chromogranin A, synaptophysin and insulin, without malignancy features (Ki 67 positive in 1% of the tumor cells). The postoperative evolution was favorable, without episodes of hypoglycemia, the fasting insulinemia one day after surgery being 4.1 µU/mL and HbA1c at three weeks postoperatively being 5.51%. Conclusions: The management of patients with hyperinsulinemic hypoglycemia secondary to insulinoma involves multidisciplinary collaboration with an important role in recognizing symptoms suggestive of hypoglycemia in a person without diabetes, initiating biological and imaging evaluation, establishing the optimal therapeutic option and histopathological confirmation.

Super paramagnetic iron oxide contrast-enhanced magnetic resonance imaging was useful in differentiating an insulinoma from an accessory spleen: a case report with review of literature

When a neuroendocrine tumor with abundant blood flow is located in the pancreatic tail, it is difficult to distinguish it from accessory spleen. The patient was a 71-year-old woman who was admitted with impaired consciousness and hypoglycemia, raising suspicion of insulinoma. The selective arterial calcium injection test suggested a lesion in the pancreatic tail. Contrast-enhanced computed tomography and magnetic resonance imaging (MRI) showed a mass in the splenic hilum; however, its continuity with the pancreas was unclear. Contrast-enhanced MRI using super paramagnetic iron oxide (SPIO) showed no SPIO uptake in the splenic hilar mass. SPIO contrast-enhanced MRI is considered useful for differentiating pancreatic endocrine tumors from paraspleen tumors.

How should we differentiate hypoglycaemia in non-diabetic patients?

Hypoglycaemic syndromes are rare in apparently healthy individuals and their diagnosis can be a difficult challenge for clinicians as there are no shared guidelines that suggest how to approach patients with a suspect hypoglycaemic disorder. Since hypoglycaemia symptoms are common and nonspecific, it's necessary to document the Whipple Triad (signs and/or symptoms compatible with hypoglycaemia; relief of symptoms following glucose administration; low plasma glucose levels) before starting any procedure. Once the triad is documented, a meticulous anamnesis and laboratory tests (blood glucose, insulin, proinsulin, C-peptide, β-hydroxybutyrate and anti-insulin antibodies) should be performed. Results can guide the physician towards further specific tests, concerning the suspected disease. In this review, we consider all current causes of hypoglycaemia, including rare diseases such as nesidioblastosis and Hirata's syndrome, describe appropriate tests for diagnosis and suggest strategies to differentiate hypoglycaemia aetiology.

Successful Localization by Hyperselective Arterial Calcium Injection Test for Surgical Resection of Insulinoma: A Case Report

Surgery is the main treatment for insulinoma, and precise preoperative localization is important to determine the extent of resection and to rule out multiple lesions. The selective arterial calcium injection (SACI) test is instrumental in the localization of insulinoma. Here we report a patient in whom the exact location of pancreatic insulinoma could not be determined by the conventional SACI test, and thus surgery was replaced with oral diazoxide. The hyperselective SACI test subsequently localized the lesion accurately, allowing surgical resection of the pancreatic body and tail while preserving the pancreatic head. We recommend the use of the hyperselective SACI test when the conventional SACI test fails to accurately determine the location of insulinoma lesions within the pancreas.

Not Just an Accident: A Case of Insulinoma

Insulinomas are a rare cause of recurrent hypoglycemia in non-diabetic patients. Diagnosis requires hypoglycemia (plasma glucose <50 mg/dL), neuroglycopenic symptoms, and prompt relief of symptoms following the administration of glucose, known as Whipple's triad. The gold standard diagnostic tests are measuring insulin, C-peptide, and glucose during a 72-hour fast. In the preoperative period and in patients with unresectable or metastatic tumors, medical management with diazoxide and octreotide can be considered for recurrent hypoglycemia. We present a case of insulinoma in a 37-year-old woman who initially presented after a seizure-related motor vehicle accident. Upon admission, her initial glucose level was 32 mg/dL, indicating a likely hypoglycemic seizure. During her hospitalization, she had recurrent episodes of fasting and postprandial hypoglycemia, ranging from 32-70 mg/dL. She exhibited the characteristics of Whipple's triad when values dropped below 50 mg/dL. These episodes necessitated continuous infusions of 10% dextrose. Tests for insulin autoantibodies, sulfonylurea screens, and thyroid function yielded unremarkable results. A 72-hour fasting test was initiated to investigate potential endogenous causes of excessive insulin production. Laboratory results from a venous glucose level of 46 mg/dL indicated a notable rise in C peptide and insulin levels, alongside beta hydroxybutyrate suppression, all of which fulfilled the diagnostic criteria for insulinoma. An abdominal magnetic resonance imaging (MRI) unveiled a 1.3 cm mass in the pancreatic tail. This case emphasizes the importance of employing a focused approach when evaluating non-diabetic individuals displaying hypoglycemia with positive Whipple's triad. This targeted method not only enables early detection of this rare condition but also assists in eliminating other common causes of recurrent hypoglycemia in non-diabetic individuals. Moreover, in addition to this diagnosis being rare, it is important to note that patients with insulinomas typically do not exhibit a glucose level low enough to induce seizures during their initial presentation.

Confirmed and presumed canine insulinomas and their presumed metastases are most conspicuous in the late arterial phase in a triple arterial phase CT protocol

Arterial enhancement is the commonly described characteristic of canine insulinomas in contrast-enhanced computed tomography (CECT). However, this finding is also reported as inconsistent. The main aim of this single-center retrospective observational study was to describe the contrast enhancement (CE) pattern of canine presumed and confirmed insulinomas and presumed metastases in three consecutive (early, mid, and late) arterial phases. Included dogs had a medical-record-based clinical or cytological/histopathological diagnosis of insulinoma and quadruple-phase CECT. The arterial phases were identified according to published literature. The arterial enhancement of confirmed and presumed lesions was assessed using a visual grading score. Twelve dogs with a total of 17 pancreatic nodules were analyzed. Three dogs had multiple pancreatic nodules and nine had solitary findings. Four insulinomas were histopathologically confirmed. Late arterial phase (LAP) images demonstrated the largest number of pancreatic nodules reaching the highest enhancement scores (n = 13, 76%). All analyzed dogs had CT evidence of arterially enhancing nodules in the liver (n = 12), seven in the hepatic, splenic, or colic lymph nodes, and three in the spleen. Three out of five sampled livers and three lymph nodes were metastatic. All sampled spleens were benign. Avid arterial enhancement was the most dominant feature of canine presumed and confirmed insulinomas and presumed metastases in quadruple-phase CECT. The highest enhancement scores were observed primarily in LAP, followed by MAP. Authors, therefore, recommend including LAP in the standard CT protocol for dogs with suspected pancreatic insulinomas.

MGACA-Net: a novel deep learning based multi-scale guided attention and context aggregation for localization of knee anterior cruciate ligament tears region in MRI images

Anterior cruciate ligament (ACL) tears are a common knee injury that can have serious consequences and require medical intervention. Magnetic resonance imaging (MRI) is the preferred method for ACL tear diagnosis. However, manual segmentation of the ACL in MRI images is prone to human error and can be time-consuming. This study presents a new approach that uses deep learning technique for localizing the ACL tear region in MRI images. The proposed multi-scale guided attention-based context aggregation (MGACA) method applies attention mechanisms at different scales within the DeepLabv3+ architecture to aggregate context information and achieve enhanced localization results. The model was trained and evaluated on a dataset of 917 knee MRI images, resulting in 15265 slices, obtaining state-of-the-art results with accuracy scores of 98.63%, intersection over union (IOU) scores of 95.39%, Dice coefficient scores (DCS) of 97.64%, recall scores of 97.5%, precision scores of 98.21%, and F1 Scores of 97.86% on validation set data. Moreover, our method performed well in terms of loss values, with binary cross entropy combined with Dice loss (BCE_Dice_loss) and Dice_loss values of 0.0564 and 0.0236, respectively, on the validation set. The findings suggest that MGACA provides an accurate and efficient solution for automating the localization of ACL in knee MRI images, surpassing other state-of-the-art models in terms of accuracy and loss values. However, in order to improve robustness of the approach and assess its performance on larger data sets, further research is needed.

Gastrinoma With Relatively Low Gastrin Levels: A Case Report

Gastrinomas can often be cured with surgical removal if detected early enough. We present a case report where a patient was diagnosed with gastrinoma with relatively low serum gastrin levels after subsequent duodenojejunostomy, gastrojejunostomy, total gastrectomy, and cholecystectomy. With this case report, we hope to promote a higher level of awareness of pancreatic neuroendocrine (NE) tumors and educate clinicians on the full effects of proton pump inhibitor (PPI) use on patient workup, diagnostics, and care.

Clinical Presentation and Diagnostic Approach to Hypoglycemia in Adults Without Diabetes Mellitus

OBJECTIVE

To review the clinical presentation, causes, and diagnostic approach to spontaneous hypoglycemia in adults without diabetes mellitus.

METHODS

A literature review was performed using the PubMed and Google Scholar databases.

RESULTS

Hypoglycemia is uncommon in people who are not on glucose-lowering medications. Under normal physiologic conditions, multiple neural and hormonal counterregulatory mechanisms prevent the development of abnormally low levels of plasma glucose. If spontaneous hypoglycemia is suspected, the Whipple triad should be used to confirm hypoglycemia before pursuing further diagnostic workup. The Whipple criteria include the following: (1) low levels of plasma glucose, (2) signs or symptoms that would be expected with low levels of plasma glucose, and (3) improvement in those signs or symptoms when the level of plasma glucose increases. Spontaneous hypoglycemia can be caused by conditions that cause endogenous hyperinsulinism, including insulinoma, postbariatric hypoglycemia, and noninsulinoma pancreatogenous hypoglycemia. Spontaneous hypoglycemia can also be seen with critical illness, hepatic or renal dysfunction, hormonal deficiency, non-diabetes-related medications, and non-islet cell tumors. The initial diagnostic approach should begin by obtaining a detailed history of the nature and timing of the patient's symptoms, medications, underlying comorbid conditions, and any acute illness. A laboratory evaluation should be conducted at the time of the spontaneous symptomatic episode. Supervised tests such as a 72-hour fast or mixed-meal test may be needed to recreate the situation under which the patient is likely to experience symptoms.

CONCLUSION

We provide an overview of the physiology of counterregulatory response to hypoglycemia, its causes, and diagnostic approaches to spontaneous hypoglycemia in adults.

Review of Hematology-Oncology Emergencies for Internal Medicine Residents

The prevalence of cancer continues to grow globally every year. With therapeutic advances over the recent decades, the prevalence of individuals living with cancer continues to increase. Internal medicine residents can see patients admitted to the hospital for cancer-related emergencies. Early identification and appropriate management of these emergencies have been shown to improve mortality and morbidity. In this article, we aim to review the recent updates in the management of commonly encountered oncologic emergencies in the practice of internal medicine residents. This review will cover spinal cord compression, superior vena cava syndrome, tumor lysis syndrome, hypercalcemia, pericardial tamponade, hypoglycemia, hyponatremia, bowel obstruction, increased intracranial pressure, leukostasis, hyperviscosity syndrome, neutropenic fever, and hypersensitivity reactions.

Pancreatic Neoplasms: CT Evaluation of the Uncommon Presentations of Common Lesions and Common Presentations of the Uncommon Lesions!

Pancreatic masses are commonly encountered entities in radiology practice. Pancreatic ductal adenocarcinomas (PDAC) are the commonest pancreatic malignancies that typically present as infiltrative hypodense focal masses in the pancreatic head, which are hypoattenuating to the pancreatic parenchyma on pancreatic parenchymal and venous phases. However, there are various atypical imaging features of PDACs that create a diagnostic dilemma like tumor in body or tail, diffuse glandular involvement, isoattenuating tumors, cystic changes, or calcifications. Also, few relatively uncommon pancreatic malignancies like pancreatic neuroendocrine tumors, cystic pancreatic tumors, pancreatic lymphoma, and pancreatic metastases present with overlapping features. Accurate radiological characterization of pancreatic masses is important for optimal management and prognostication. Thus, it is imperative for radiologists to be aware of all the uncommon presentations of common pancreatic lesions and common presentations of uncommon pancreatic lesions to avoid erroneous interpretations and establishing the correct diagnosis.

Metastatic insulinoma presenting with post-prandial hypoglycemia

Background/Objective

Patients with an insulinoma, a type of pancreatic neuroendocrine tumor, typically present with fasting hypoglycemia but can rarely present exclusively with postprandial hypoglycemia.

Case Report

A 69-year-old man presented with episodes of postprandial blurry vision, sweating, and confusion for the last 2 years that were becoming more frequent over the last several weeks. Home blood glucose measurements revealed postprandial hypoglycemia (glucose level, 45-70 mg/dL), and symptoms were consistent with the Whipple triad. Continuous glucose monitoring revealed only postprandial hypoglycemia within 2 hours following meals. An outpatient fast was conducted with detectable insulin (6 μIU/mL) and C-peptide (2.0 ng/mL) levels with an elevated proinsulin (20.8 pmol/L) level when the serum blood glucose level dropped to 47 mg/dL (21 hours after the initiation of the fast). A computed tomography scan of the abdomen and pelvis showed a 1.6-cm hyperenhancing lesion in the distal body of the pancreas. He underwent endoscopic ultrasonography with fine-needle aspiration. Pathology revealed a low-grade, well-differentiated, neuroendocrine tumor with lymphovascular invasion and regional lymph node metastases, confirming the diagnosis of a pancreatic neuroendocrine tumor.

Discussion

Exclusive postprandial hypoglycemia is estimated to occur in 6% of the insulinomas. Patients with postprandial hypoglycemia may be initially managed as those with reactive hypoglycemia; however, this case highlights the importance of evaluating for an insulinoma in a patient who has failed treatment for reactive hypoglycemia. This case also demonstrates the importance of including proinsulin levels in that evaluation.

Conclusion

Pancreatic neuroendocrine tumor should be considered in postprandial hypoglycemia, even in the absence of fasting hypoglycemia. Measuring proinsulin levels is essential in the diagnostic workup of insulinoma causing hypoglycemia.

Adult-Onset Focal Nesidioblastosis With Nodular Formation Mimicking Insulinoma

Nesidioblastosis is defined as the neoformation of the islets of Langerhans from the pancreatic ductal epithelium and is recognized as the most common cause of hyperinsulinemic hypoglycemia in infants. We herein report an extremely rare case of adult-onset focal nesidioblastosis with the unusual feature of hyperplastic nodular formation. A 55-year-old woman was admitted to our hospital for a tumor detected in the body of the pancreas by magnetic resonance imaging screening. Laboratory examinations showed a high insulin level in the blood. Contrast-enhanced computed tomography and the selective arterial calcium injection test suggested the presence of multiple insulinomas in the body and tail of the pancreas, and, thus, the patient underwent distal pancreatectomy. A histopathological examination of the tumor in the body of the pancreas showed the nodular hyperplasia of islet-like cell clusters. In addition, many small intralobular ductules and islet cells appeared to be budding from the proliferating ductal epithelium, forming “ductuloinsular complexes”. No other abnormal lesion was detected in the remainder of the pancreas. The histopathological diagnosis was focal nesidioblastosis. The patient has remained free of the recurrence of hypoglycemic episodes for more than 31 months. The present case of rare adult-onset focal nesidioblastosis with hyperplastic nodular formation was preoperatively identified as an apparent pancreatic tumor mimicking insulinoma. Nesidioblastosis and insulinoma need to be considered in cases of hyperinsulinemic hypoglycemia, even in adult patients.

Management recommendations for pancreatic manifestations of von Hippel-Lindau disease

Von Hippel-Lindau disease (VHL) is a multineoplasm inherited disease manifesting with hemangioblastoma of the central nervous system and retina, adrenal pheochromocytoma, renal cell carcinoma, pancreatic neuroendocrine tumors and cysts, and neoplasms/cysts of the ear, broad ligament, and testicles. During 2018-2020, the VHL Alliance gathered several committees of experts in the various clinical manifestations of VHL to review the literature, gather the available evidence on VHL, and develop recommendations for patient management. The current report details the results of the discussion of a group of experts in the pancreatic manifestations of VHL along with their proposed recommendations for the clinical surveillance and management of patients with VHL. The recommendations subcommittee performed a comprehensive systematic review of the literature and conducted panel discussions to reach the current recommendations. The level of evidence was defined according to the Shekelle variation of the Grading of Recommendations, Assessment, Development, and Evaluation grading system. The National Comprehensive Cancer Network Categories of Evidence and Consensus defined the committee members' interpretation of the evidence and degree of consensus. The recommendations encompass the main aspects of VHL-related pancreatic manifestations and their clinical management. They are presented in a clinical orientation, including general planning of screening and surveillance for pancreatic neuroendocrine tumors, utility of biochemical biomarkers, the optimal choice for imaging modality, indirect risk stratification, indications for tissue sampling of VHL-related pancreatic neuroendocrine tumors, and interventions. These recommendations are designed to serve as the reference for all aspects of the screening, surveillance, and management of VHL-related pancreatic manifestations.

Concomitant intraductal papillary mucinous neoplasm (IPMN) and neuroendocrine tumor (NET) of pancreas

We present a rare clinical case of a 66-year-old woman who had two different synchronuos tumors of pancreas: intraductal papillary mucinous neoplasm (IPMN) and neuroendocrine cancer. The preoperative CT/MRI diagnosis was not too difficult, because of the typical presentations, but the combination of features was very unusual. A morphological examination after surgical operation followed by fine-needle biopsy confirmed the preoperative diagnosis of combined the two different tumors.

The appearance of canine insulinoma on dual phase computed tomographic angiography

OBJECTIVES

To further evaluate the appearance of insulinoma in dogs on dual-phase CT angiography, given the disparity of findings in recent publications. To establish whether CT angiographic localisation of insulinoma correlates with surgical findings.

MATERIALS AND METHODS

Single centre study of dogs with a final diagnosis of insulinoma which underwent abdominal CT angiography. Scans were retrospectively re-evaluated for specific features by two board-certified veterinary radiologists. These findings were also subsequently compared to surgical and histopathological reports to determine the accuracy of lesion localisation on CT.

RESULTS

Thirty-five cases were included in final analysis, with pancreatic nodules identified in 33. Twenty-one were confirmed as insulinoma with histopathology. Jack Russell Terriers were over-represented. Twenty of 21 cases with confirmed insulinoma and 27 of 33 overall showed hyperattenuation in the arterial phase. The mean size of pancreatic insulinoma on CT was 15.1 mm, and 18.2% were larger than 20 mm. Eighteen of 21 confirmed and eight of 12 suspected insulinomas caused a deformation of the pancreatic shape, with two only identified as a result of this feature as these lesions were isoattenuating throughout the study. Pancreatic insulinoma location at surgery matched that described on the CT images in 17 of 19 cases where location was described in the surgical report.

CLINICAL SIGNIFICANCE

In contrast to recent publications, this study suggests hyperattenuation of insulinomas in the arterial phase is a predominant feature, and that hypoattenuation or isoattenuation are much less common. CT angiography is accurate in prediction of lesion location before surgery in most cases.

Multiple Endocrine Neoplasia Type 1 and the Pancreas: Diagnosis and Treatment of Functioning and Non-Functioning Pancreatic and Duodenal Neuroendocrine Neoplasia within the MEN1 Syndrome - An International Consensus Statement

The better understanding of the biological behavior of multiple endocrine neoplasia type 1 (MEN1) organ manifestations and the increase in clinical experience warrant a revision of previously published guidelines. Duodenopancreatic neuroendocrine neoplasias (DP-NENs) are still the second most common manifestation in MEN1 and, besides NENs of the thymus, remain a leading cause of death. DP-NENs are thus of main interest in the effort to reevaluate recommendations for their diagnosis and treatment. Especially over the last 2 years, more clinical experience has documented the follow-up of treated and untreated (natural-course) DP-NENs. It was the aim of the international consortium of experts in endocrinology, genetics, radiology, surgery, gastroenterology, and oncology to systematically review the literature and to present a consensus statement based on the highest levels of evidence. Reviewing the literature published over the past decade, the focus was on the diagnosis of F- and NF-DP-NENs within the MEN1 syndrome in an effort to further standardize and improve treatment and follow-up, as well as to establish a "logbook" for the diagnosis and treatment of DP-NENs. This shall help further reduce complications and improve long-term treatment results in these rare tumors. The following international consensus statement builds upon the previously published guidelines of 2001 and 2012 and attempts to supplement the recommendations issued by various national and international societies.

Multiple Endocrine Neoplasia: Spectrum of Abdominal Manifestations

OBJECTIVE. Multiple endocrine neoplasia (MEN) syndromes are autosomal-dominant genetic disorders that predispose two or more organs of the endocrine system to tumor development. Although the diagnosis relies on clinical and serologic findings, imaging provides critical information for surgical management with the ultimate goal of complete tumor resection. CONCLUSION. This article reviews abdominal neoplasms associated with the various subtypes of MEN syndromes, with a focus on clinical presentation and characteristic imaging features.

Vasoactive Intestinal Peptide-Secreting Tumors: A Review

Vasoactive intestinal peptide-secreting tumors (VIPomas) are a group of rare neuroendocrine tumors, which cause a typical syndrome of watery diarrhea. Most of these tumors are found in the pancreas and are usually detected at a later stage. Although curative resection is not possible in most of these tumors, both symptom and tumor control can be achieved by a multidimensional approach, to enable a long survival of most patients. There are no clear-cut guidelines for the management of VIPomas because of the rarity of this neoplasm and lack of prospective data. In this review, we discuss the available evidence on the clinical features and management of these rare tumors.

Comparison of desferrioxamine and NODAGA for the gallium-68 labeling of exendin-4

INTRODUCTION

Radiolabeled exendin-4 (Ex4) derivatives are used to target the glucagon-like peptide-1 receptor (GLP-1R) for the clinical diagnosis of insulinomas, a rare type of neuroendocrine tumor. Gallium-68 is an ideal diagnostic nuclide for this application and a study evaluating an exendin-4-NODAGA conjugate is currently underway. However, in complexion with the chelator DFO, its in vivo stability has been a matter of dispute. The aim of this work was to directly compare [⁶⁸Ga]Ga-Ex4NOD with [⁶⁸Ga]Ga-Ex4DFO in vitro and in vivo.

METHODS

In our approach, we directly compared N'-[5-(acetyl-hydroxy-amino)pentyl]-N-[5-[3-(5-aminopentyl-hydroxy-carbamoyl)propanoylamino]pentyl]-N-hydroxy-butane diamide (desferriox-amine B, DFO) and 2-(4,7-bis (carboxymethyl)-1,4,7-triazonan-1-yl) pentanedioic acid (NODAGA) conjugated to exendin-4 in vitro and in vivo. We radiolabeled the peptides with gallium-68, followed by HPLC quality control. In vitro characterization was performed in CHL cells overexpressing the GLP-1R and in vivo studies were conducted with CD1 nu/nu mice carrying tumors derived from these cells.

RESULTS

We found that both peptides could be radiolabeled with a molar activity of about 9.33 MBq/nmol without further purification. They internalized equally well into GLP-1R-expressing cells and their IC₅₀ was similar with 15.6 ± 7.8 nM and 18.4 ± 3.0 nM for [^natGa]Ga-Ex4NOD and [^natGa]Ga-Ex4DFO, respectively. In vivo, [⁶⁸Ga]Ga-Ex4NOD accumulated more in all tissue, while [⁶⁸Ga]Ga-Ex4DFO exhibited a more favorable target-to-kidney ratio.

CONCLUSION AND RELEVANCE

DFO is a suitable chelator for the radiolabeling of exendin-4 derivatives with gallium-68 for in vitro and preclinical in vivo studies. DFO performed better in vivo due to its significantly lower kidney accumulation (p < 0.0001). It was also found to be stable in vivo in mice, contrary to earlier reports. Based on our results, the DFO chelating system in combination with exendin-4 would be an interesting option for clinical imaging of insulinomas.

Differentiation of hypovascular pancreatic neuroendocrine tumors from pancreatic ductal adenocarcinoma using contrast-enhanced computed tomography

Hypovascular pancreatic neuroendocrine tumors (hypo-PNETs) are often misdiagnosed as pancreatic ductal adenocarcinoma (PDAC). However, the treatment options and prognosis of PNETs and PDAC are substantially different. This retrospective study differentiated hypo-PNETs from PDAC using contrast-enhanced CT (CE-CT). Clinical data and CE-CT findings, including tumor location, size, boundary, pancreatic duct dilatation, local invasion or metastases, tumor contrast enhancement, and tumor-to-pancreas enhancement ratio, were compared between 39 PDACs and 18 hypo-PNETs. At CT imaging, hypo-PNETs showed a higher frequency of a well-defined margin and lower frequencies of pancreatic duct dilatation and local invasion or metastasis when compared with PDAC (p < 0.05 for all). The mean attenuation of hypo-PNETs at the arterial and portal venous phase was significantly higher than that of PDAC (p < 0.001, p = 0.003, respectively). Similar results were observed in tumor-to-pancreas enhancement ratio. Tumor attenuation and tumor-to-pancreas enhancement ratio at the arterial phase showed the largest area under the curve (AUC) of 0.888 and 0.812 with 83.3-88.9% of sensitivity and 61.6-77.0% of specificity. Pancreatic duct dilatation, local invasion or metastasis, and tumor attenuation at the portal venous phase also showed acceptable AUC (0.703-0.748). Thus CE-CT features, especially the enhancement degree at the arterial phases, may be useful for differentiating hypo-PNETs from PDAC using CE-CT.

Canine insulinomas appear hyperintense on MRI T2-weighted images and isointense on T1-weighted images

Clinical and imaging diagnosis of canine insulinomas has proven difficult due to nonspecific clinical signs and the small size of these tumors. The aim of this retrospective case series study was to describe MRI findings in a group of dogs with pancreatic insulinomas. Included dogs were presented for suspected pancreatic insulinoma, MRI was used to assist with localization of the primary lesion, and the diagnosis was confirmed with surgical exploratory laparotomy and histopathology. The MRI studies for each dog were retrieved and the following data were recorded: T1-weighted and T2-weighted signal intensities, type of contrast enhancement, size and location of the primary lesion, and characteristics of metastatic lesions (if present). A total of four dogs were sampled. In all patients, the insulinoma displayed high-intensity signal on T2-weighted fat saturation images, similar to human studies. On postcontrast T1-weighted fat saturation images, the tumors were primarily isointense to normal pancreatic tissue, in contrast to human studies where a low-intensity signal is typically identified. Abnormal islet tissue was detected with MRI in all four dogs and metastases were identified in three dogs. Variations in the MRI appearance of primary and metastatic lesions were identified and could have been related to the variation of tissue composition, including the presence of neoplastic cells, hemorrhage, and fibrovascular stroma, and to the transformation of this tissue throughout the disease process.

A case of hyperinsulinemic hypoglycemia related with a calcimimetic agent

We herein report a case of a 60-year-old female receiving hemodialysis who developed severe hyperinsulinemic hypoglycemia and lost her consciousness. A calcimimetic agent had been administered for the secondary hyperparathyroidism. The calcimimetic agent, mimicking the elevation of the extracellular calcium ion concentration, activates calcium-sensing receptors (CaSR) of the parathyroid cells and inhibits the parathyroid hormone secretions. The previous study suggested that the CaSR are also expressed in both human β cells and insulinoma cells, but the reactivity to change in the extracellular calcium ion concentration is different between normal β cells and insulinoma cells. After cessation of the calcimimetic agent, hypoglycemic symptoms disappeared and endogenous insulin secretion dropped to normal levels. However, the result of a prolonged fasting test indicated that she remained hyperinsulinemic even after its cessation, suggesting that she had insulinoma which could not be detected by the imaging examinations. The previous autopsy data showed that there were many cases of the insulinoma without the symptoms of hypoglycemia. We considered the possibility that she had the insulinoma and the pancreatic tumor was too small to promote the insulin secretion and cause hypoglycemia without activation by the calcimimetic agent. We should know that the calcimimetic agent could cause hyperinsulinemic hypoglycemia with the unidentified insulinoma.

Homogenously isoattenuating insulinoma on biphasic contrast-enhanced computed tomography: Little benefits of diffusion-weighted imaging for lesion detection

The aim of the present study was to evaluate the diagnostic benefit of diffusion-weighted imaging (DWI) in the detection of homogenous isoattenuating insulinoma on biphasic contrast-enhanced computed tomography (CT) preoperatively and to determine which magnetic resonance (MR) sequences exhibited the best diagnostic performance. A total of 44 consecutive patients who underwent biphasic contrast-enhanced CT and conventional MR imaging (MRI), including DWI on a 3T scanner, were identified retrospectively. Apparent diffusion coefficient (ADC) values of insulinomas and the surrounding pancreatic parenchyma were compared using a Wilcoxon signed-rank test. Receiver operating characteristic analysis was used to compare the diagnostic accuracy of four randomized image sets [T2-weighted image (WI), axial T1WI, DWI and T2WI + DWI] for each reader. Axial T1-weighted MRI exhibited the highest relative sensitivity for each reader; DWI alone exhibited the lowest relative sensitivity and the lower inter-reader agreement. There was no significant difference in lesion detection between T2WI and T2WI + DWI image sets for each reader. The ADC values of the insulinoma were significantly lower compared with those of the surrounding parenchyma. In conclusion, DWI does not benefit the detection of homogenous isoattenuating insulinoma. Axial T1WI is the optimal pulse sequence. Quantitative assessment of the tumor ADC values may be a useful tool to characterize identified pancreatic neoplasms.

EUS-guided lauromacrogol ablation of insulinomas: a novel treatment

BACKGROUND AND AIMS

EUS-guided ablation with ethanol has been used to treat insulinoma since 2006 as a minimally invasive alternative for those who are unwilling or unsuitable for surgeries. However, pancreatic fistula, pancreatitis and other adverse effects were found after the procedure in these patients. Herein, we aimed to find a novel feasible injection.

METHODS

Seven patients with different chief complaints were diagnosed with insulinoma by symptoms, lab results and pathology results from EUS fine needle aspiration. All the patients refused to have surgeries and were treated by EUS-guided ablation with lauromacrogol. The injection volume was calculated by tumor size. All the patients were followed up by at least 1 month to see if there is any adverse effect. Blood glucose (BG), insulin and C-peptide levels were monitored before and after the procedure.

RESULTS

Insulinoma size ranged from 0.76 cm ×0.84 cm to 3.39 cm ×1.84 cm. With a mean injection volume of 1.9 ml (range from 0.9 to 3.9 ml), all the patients showed relief in symptoms after the procedure. During the follow up, their BG, insulin and C-peptide levels went back to normal. None of the patients had any adverse effect.

CONCLUSIONS

EUS-guided ablation with lauromacrogol showed good treatment results and received no adverse effect after the procedure. Hence, we consider it as an effective and safe method to treat insulinoma.

Radiosynthesis and evaluation of an 18F-labeled silicon containing exendin-4 peptide as a PET probe for imaging insulinoma

Background

Analogues of exendin-4 have been radiolabeled for imaging the glucagon-like peptide type 1 receptors (GLP-1R) which are overexpressed in insulinoma. The aim of this research was to synthesize an ¹⁸F–labeled silicon containing exendin-4 peptide (¹⁸F-2) and to evaluate its in vitro and in vivo behavior in CHL-GLP-1 receptor positive tumor-bearing mice.

¹⁸F–labeled silicon containing exendin-4 peptide (¹⁸F-2) was prepared via one-step nucleophilic substitution of a silane precursor with ¹⁸F–fluoride in the presence of acetic acid and K222. ¹⁸F-2 was then administered to tumor-bearing mice for PET imaging and ex vivo biodistribution experiments.

Results

¹⁸F-2 was produced in a radiochemical yield (decay corrected) of 1.5% and a molar activity of max. 16 GBq/μmol. The GLP-1R positive tumors were clearly visualized by PET imaging. Biodistribution studies showed reduced uptake of ¹⁸F-2 in the kidneys compared to radiometal labeled exendin-4 derivatives. The radiotracer showed specific tumour uptake which remained steady over 2 h.

Conclusions

This exendin-4 analogue, ¹⁸F-2, is a potential probe for imaging GLP-1R positive tumors.

"Riding High on Low Fuel" - Our Experience with Endogenous Hyperinsulinemic Hypoglycemia

INTRODUCTION

Endogenous hyperinsulinemic hypoglycemia (EHH) is a condition in which the insulin levels are inappropriately high in the presence of low plasma glucose.

MATERIALS AND METHODS

We did a retrospective analysis of case records of those patients admitted and evaluated for EHH from June 2004 to June 2016 in our center, excluding those that were diagnosed with reactive hypoglycemia. We collected data regarding demographics, clinical presentation, laboratory results, localization techniques, and treatment administered.

RESULTS

Sixteen patients who were admitted for evaluation based on history suggestive of repeated hypoglycemic episodes were included in the study. All but one pregnant patient was subjected to a supervised fast in the hospital. All patients developed hypoglycemia (defined using Whipple's triad) within the first 24 h. Three patients had autoimmune hypoglycemia which differed significantly from insulinoma-mediated hypoglycemia in certain clinical and laboratory parameters. They were older in age with marked fluctuations in the 24 h glucose profile ranging from frank hypoglycemia to frank hyperglycemia. The insulin levels were markedly elevated in this group of patients along with a significantly elevated insulin C peptide molar ratio (ICMR) when compared with patients with insulinoma-mediated hypoglycemia.

CONCLUSIONS

Although insulinoma is the most common cause of EHH, autoimmune hypoglycemia should be considered as a differential diagnosis, particularly in older individuals with plasma glucose values increasing to the hyperglycemic range. Degree of elevation of insulin levels and ICMR may provide additional clues. Overall, the survival and prognosis of patients with EHH are excellent.

Pancreatic Imaging

Imaging of the endocrine pancreas is dominated by neuroendocrine tumors, a diverse category of neoplasms that may or may not cause symptoms from hormone hypersecretion. These tumors may also be evidence of several different genetic syndromes. Understanding the usefulness of different imaging modalities and entities that simulate neuroendocrine tumors is key for both radiologists and referring physicians.

MANAGEMENT OF ENDOCRINE DISEASE: Pathogenesis and management of hypoglycemia

Glucose is the main substrate utilized by the brain and as such multiple regulatory mechanisms exist to maintain glucose concentrations. When these mechanisms fail or are defective, hypoglycemia ensues. Due to these robust mechanisms, hypoglycemia is uncommon and usually occurs in the setting of the treatment of diabetes using glucose-lowering agents such as sulfonylureas or insulin. The symptoms of hypoglycemia are non-specific and as such it is important to confirm hypoglycemia by establishing the presence of Whipple's triad before embarking on an evaluation for hypoglycemia. When possible, evaluation of hypoglycemia should be carried out at the time of spontaneous occurrence of symptoms. If this is not possible then one would want to create the circumstances under which symptoms occur. In cases where symptoms occur in the post absorptive state, a 72-h fast should be performed. Likewise, if symptoms occur after a meal then a mixed meal study may be the test of choice. The causes of endogenous hyperinsulinemic hypoglycemia include insulinoma, post-bariatric hypoglycemia and noninsulinoma pancreatogenous hypoglycemia syndrome. Autoimmune hypoglycemia syndrome is clinically and biochemically similar to insulinoma but associated with high levels of insulin antibodies and plasma insulin. Other important causes of hypoglycemia include medications, non-islet cell tumors, hormonal deficiencies, critical illness and factitious hypoglycemia. We provide an overview of the pathogenesis and management of hypoglycemia in these situations.

Comparison of Ultrasonography and Low-Dose Computed Tomography for the Diagnosis of Pediatric Urolithiasis in the Emergency Department

OBJECTIVE

This study aimed to compare ultrasonography (US) and low-dose computed tomography (LDCT) for diagnosing pediatric urolithiasis in the emergency department.

MATERIALS AND METHODS

This retrospective study was approved by our institutional ethics committee, and informed consent was waived. From March 2016 to March 2017, 100 consecutive patients met the selection criteria and were enrolled in the study. Patients were randomly selected in a 1:1 ratio and were allocated to one of the following two imaging groups: US or abdominal LDCT. LDCT examinations were performed using a 320-detector row CT. Radiation dose analysis was performed using Radimetrics. US examinations were performed using the Aplio 500 ultrasound system. The presence of urolithiasis, anatomical location of urolithiasis, and measurements of renal stones were evaluated and recorded.

RESULTS

There were statistically significant differences between US and standard-dose CT (SDCT) with respect to the diagnosis of urolithiasis, anatomical location of urolithiasis, and measurements of renal stones (p<0.001, p=0.005, and p=0.03, respectively). The mean effective radiation dose of LDCT was 1.44±0.34 mSv and that of SDCT was calculated to be 4.36±1.33 mSv. There was no statistically significant difference between LDCT and SDCT with regard to the diagnosis of urolithiasis, anatomical location of urolithiasis and measurements of renal stones (p=1 for all). The diagnostic accuracy of US and LDCT was 0.68 and 1.0, respectively.

CONCLUSION

Low-dose computed tomography had 1/3 SDCT radiation dose, and LDCT and SDCT accurately diagnosed pediatric urolithiasis in the emergency department. US had a lower accuracy than SDCT and LDCT for diagnosing pediatric urolithiasis in the emergency department. LDCT can be an alternative for SDCT for diagnosing pediatric urolithiasis.

Characterization of single lesion nonfunctioning pancreatic neuroendocrine carcinoma via computed tomography

Nonfunctioning pancreatic neuroendocrine carcinoma (NPNEC) is a poorly differentiated neuroendocrine carcinoma and a rare type of pancreatic cancer. Computed tomography (CT)-based imaging is currently the most effective method for diagnosing and classifying NPNEC. The present study investigated the clinical features and CT manifestations of this disease. The CT manifestations and clinical data of 13 patients with NPNEC, confirmed by surgery or needle biopsy, were retrospectively analyzed. None of the 13 patients exhibited endocrine-related symptoms and a single lesion with a variable position in the pancreatic was observed in all patients. The tumors were generally round or irregular, with inhomogeneous density and an average diameter of 7.45±3.92 cm (range, 4.0–16.0 cm). Cystic necrosis zones were observed in 5 patients and calcification was observed in 2. A total of 4 patients exhibited intrahepatic metastases, and 2 patients demonstrated spleen and colon invasion. Enhanced scanning indicated that tumors were markedly enhanced. There were 11 cases of middle or high-grade enhancement (84.6%) and 2 cases of mild enhancement (15.4%). Marked envelope enhancement was observed in 3/11 patients with high-grade enhancement. In conclusion, the majority of patients with NPNEC lacked characteristic manifestations. While the CT examination revealed certain characteristics, histological analysis was necessary to confirm diagnoses.

Prospective comparison of biphasic contrast-enhanced CT, volume perfusion CT, and 3 Tesla MRI with diffusion-weighted imaging for insulinoma detection

PURPOSE

To evaluate the diagnostic performance of biphasic contrast-enhanced CT (CECT), volume perfusion CT (VPCT) and 3 Tesla MRI with diffusion-weighted imaging (DWI), in patients with clinically suspected insulinomas.

MATERIALS AND METHODS

This prospective study was approved by the institutional review board. Sixty-four patients with clinically suspected insulinomas underwent biphasic CECT, VPCT, and 3T MR with DWI. Two radiologists independently determined the presence/absence of tumor using a 5-scale confidence level. Conspicuity of the lesion and clarity of tumor-to-pancreatic duct distance were graded. Receiver operating characteristic analysis was performed to compare diagnostic performance.

RESULTS

Forty-seven patients were tumor positive, with 51 tumors. The differences between the areas under the curve values for tumor detection were as follows: 0.715 (CECT), 0.903 (VPCT), 0.832 (MRI without DWI) and 0.955 (MRI with DWI) for reader 1, and 0.738 (CECT), 0.895 (VPCT), 0.841 (MRI without DWI), and 0.956 (MRI with DWI) for reader 2. MRI with DWI and VPCT were significantly more accurate than CECT for insulinoma detection (P = 0.01 and 0.02 for reader 1, and P = 0.01 and 0.03 for reader 2). Lesion conspicuity was better on MRI compared with VPCT (P = 0.01), and both were better than CECT (both P < 0.01). Tumor-to-pancreatic duct distance was better appreciated on MRI, compared with CECT and VPCT (both P < 0.01). The weighted k values indicate good to excellent agreement between observers for determining tumor presence/absence (k = 0.64-0.84).

CONCLUSION

The 3T MRI with DWI and VPCT are significantly more accurate than CECT for insulinoma detection. MRI demonstrates higher tumor conspicuity and is superior in depicting the tumor-to-duct distance.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1648-1655.

Vascularity and Tumor Size are Significant Predictors for Recurrence after Resection of a Pancreatic Neuroendocrine Tumor

BACKGROUND

It is difficult to identify patients at high risk of recurrence after pancreatectomy for pancreatic neuroendocrine tumor (PNET) using only the grading classification, especially the G2 category, which includes both benign and low- and high-grade malignant tumors.

METHODS

Forty-one patients with PNET who underwent pancreatectomy were enrolled in this study. We defined the computed tomography (CT) ratio as the CT value of the tumor divided by that of non-tumorous pancreatic parenchyma using the late arterial phase dynamic CT. The optimal cut-off values for CT ratio and tumor size were determined using p-values that were calculated using the log-rank test.

RESULTS

The optimal cut-off values of CT ratio and tumor size for dividing patients into groups according to the greatest difference in disease-free survival (DFS) were 0.85 (p < 0.001) and 3.0 cm (p < 0.001), respectively. In analysis using Spearman's correlation coefficient, CT ratio (p = 0.007) and tumor size (p = 0.003) were individually associated with the Ki-67 proliferative index. Cox proportional hazard analysis identified that a CT ratio <0.85 (n = 10, p = 0.006) and tumor size ≥3.0 cm (n = 13, p = 0.023) were independent prognostic factors associated with DFS. All patients in the CT ratio ≥0.85 and tumor size <3.0 cm group (n = 23, including seven patients with G2 disease) did not develop recurrence after surgery. On the other hand, 5-year DFS in the CT ratio <0.85 and tumor size ≥3.0 cm group (n = 5, including three patients with G2 disease) was zero.

CONCLUSIONS

PNETs with a CT ratio <0.85 and tumor size ≥3.0 cm should be considered as having a high risk of recurrence after pancreatectomy.

Cross sectional and nuclear medicine imaging of pancreatic insulinomas

Insulinomas are rare neuroendocrine tumors which occur predominantly in the pancreas. Although majority of the insulinomas are benign, over-secretion of insulin by the tumor leads to debilitating hypoglycemic symptoms. The diagnosis is based on clinical and biochemical findings. After the diagnosis is made, the principal challenge lies in locating the tumor because most tumors are solitary and small in size. Locating the tumor is of paramount importance as complete surgical excision is the only curative treatment, and incomplete resection leads to persistence of symptoms. Different preoperative and intraoperative imaging techniques have been used with varying success rates for the insulinoma imaging. Besides localizing the tumor, imaging also helps to guide biopsy, detect metastatic lesions, and perform image-guided therapeutic procedures. This review will discuss the role of different Cross sectional and nuclear medicine imaging modalities in insulinomas.

Association of Insulinoma and Type 2 Diabetes Mellitus

The association of diabetes mellitus and insulinoma is unusual. We are reporting the case of a 58 years old patient having diabetes mellitus type 2 for several years. This patient was well balanced with oral anti-diabetic treatment. However, the diagnosis of insulinoma was discussed due to recent episodes of hypoglycemia that persisted even after stopping the treatment. Abdominal CT allowed the topographic diagnosis. The patient underwent a caudal pancreatectomy. Furthermore, the postoperative period shows that the diabetes mellitus requires the oral anti-diabetic treatment and basal insulin have to be stable. Then, the occurrence of hypoglycemia in the diabetic mellitus type 2 and, especially the persistence after discontinuation of therapy, suggest the unusual diagnosis of insulinoma as illustrated in our observation.

Neuroendocrine Tumors

Neuroendocrine tumors are increasingly diagnosed, either incidentally as part of screening processes, or for symptoms, which have commonly been mistaken for other disorders initially. The diagnostic workup to characterize tumor behaviour and prognosis focuses on histologic, anatomic, and functional imaging assessments. Several therapeutic options exist for patients ranging from curative and debulking surgery through to liver-directed therapies and systemic treatments. Multimodal therapies are often required over the patient's disease history. The management paradigm can be complex but should be focused on curative resections and then on controlling symptoms and limiting disease progression. There are several new systemic therapies that have completed phase 3 studies with new compounds being studied in phase 2. Genetic and epigenetic markers may lead to a new era of personalised therapy in the future.

99mTc Labeled Glucagon-Like Peptide-1-Analogue (99mTc-GLP1) Scintigraphy in the Management of Patients with Occult Insulinoma

INTRODUCTION

The aim of this study was to assess the utility of [Lys40(Ahx-HYNIC-99mTc/EDDA)NH2]-exendin-4 scintigraphy in the management of patients with hypoglycemia, particularly in the detection of occult insulinoma.

MATERIALS AND METHODS

Forty patients with hypoglycemia and increased/confusing results of serum insulin and C-peptide concentration and negative/inconclusive results of other imaging examinations were enrolled in the study. In all patients GLP-1 receptor imaging was performed to localise potential pancreatic lesions.

RESULTS

Positive results of GLP-1 scintigraphy were observed in 28 patients. In 18 patients postsurgical histopathological examination confirmed diagnosis of insulinoma. Two patients had contraindications to the surgery, one patient did not want to be operated. One patient, who presented with postprandial hypoglycemia, with positive result of GLP-1 imaging was not qualified for surgery and is in the observational group. Eight patients were lost for follow up, among them 6 patients with positive GLP-1 scintigraphy result. One patient with negative scintigraphy was diagnosed with malignant insulinoma. In two patients with negative scintigraphy Munchausen syndrome was diagnosed (patients were taking insulin). Other seven patients with negative results of 99mTcGLP-1 scintigraphy and postprandial hypoglycemia with C-peptide and insulin levels within the limits of normal ranges are in the observational group. We would like to mention that 99mTc-GLP1-SPECT/CT was also performed in 3 pts with nesidioblastosis (revealing diffuse tracer uptake in two and a focal lesion in one case) and in two patients with malignant insulinoma (with the a focal uptake in the localization of a removed pancreatic headin one case and negative GLP-1 1 scintigraphy in the other patient).

CONCLUSIONS

99mTc-GLP1-SPECT/CT could be helpful examination in the management of patients with hypoglycemia enabling proper localization of the pancreatic lesion and effective surgical treatment. This imaging technique may eliminate the need to perform invasive procedures in case of occult insulinoma.

Preoperative localization of an insulinoma: selective arterial calcium stimulation test performance

PURPOSE

Preoperative localization of an insulinoma is recommended to improve the cure rate, but non-invasive procedures can fail to detect the tumour. The objective of the study was to assess the performance of a selective arterial calcium stimulation test in the preoperative localization of insulinomas that were not detected by conventional imaging procedures.

METHODS

We conducted a monocenter retrospective case review of 13 patients who had endogenous hyperinsulinism and were treated between 1994 and 2013. Patients were selected on the basis of negative or doubtful non-invasive preoperative imaging. A selective arterial calcium stimulation test was performed by pancreatic and hepatic arteriography with selective intra-arterial calcium stimulation and hepatic venous sampling in order to obtain the plasma insulin measurement. We evaluated the efficacy of the test by comparing the results with an endoscopic ultrasound.

RESULTS

Twelve of the 13 patients underwent surgery, and the presence of an insulinoma was proven in 11 patients by pathological analysis of the tumour. An endoscopic ultrasound was consistent with surgery in 71.4 % of cases, while selective arterial calcium stimulation was consistent with surgery in 90.9 % and allowed detection of an insulinoma in two additional patients with a negative endoscopic ultrasound. One false-negative and one false-positive arterial calcium test were observed. No adverse events were recorded except transient skin flush following calcium injection in one patient.

CONCLUSION

The selective arterial calcium stimulation test is a sensitive diagnostic procedure for localizing insulinomas and may be considered when non-invasive radiological imaging does not allow the detection of an occult insulinoma.

Role of (68)Ga somatostatin receptor PET/CT in the detection of endogenous hyperinsulinaemic focus: an explorative study

PURPOSE

To explore the role of (68)Ga-DOTATATE/DOTATOC PET/CT (SR PET/CT) in patients with suspicion of or histopathologically proven pancreatogenic hyperinsulinaemic hypoglycaemia.

METHODS

We included 13 patients with histopathologically proven or a high clinical suspicion of pancreatogenic hyperinsulinaemia. All the patients underwent a SR PET/CT scan. The results were correlated with histopathological findings. Normalization of blood glucose levels after resection of the pancreatic lesion, as well as a cytological and/or pathological diagnosis of insulinoma, was considered the diagnostic gold standard for insulinoma. The diagnosis of nesidioblastosis was based on exclusion of an insulinoma and conclusive pathological examination of a segment of the pancreas. Malignant insulinoma was defined as the presence of locoregional or distant metastases.

RESULTS

Based on histopathology, 13 patients were found to have pancreatic hyperinsulinaemia: two patients had malignant insulinoma, eight had nonmetastasized insulinoma, and three had nesidioblastosis. SR PET was positive in 11 of the 13 patients (84.6 %) with a final diagnosis of endogenous pancreatic hypoglycaemia. Histopathological staining confirmed 16 foci of hyperinsulinism (insulin positivity). SR PET detected 14 of the 16 lesions, resulting in a sensitivity of 87 %. One intrapancreatic spleen was falsely diagnosed as insulinoma focus on SR PET, resulting in positive predictive value of 93.3 %. Immunohistochemical staining of somatostatin receptor (SSR) subtype 2a was available in ten specimens: two nesidioblastosis, and seven benign and one malignant insulinoma. Eight out of the ten specimens (80 %) stained strongly to moderately positive. Seven of the eight SSR2a-positive lesions were picked up on SR PET. Based on the results of SR PET/CT, nine patients achieved complete remission of the hypoglycaemic events during follow-up.

CONCLUSION

This explorative study suggests that SR PET in combination with CT may play a significant role in the detection and management of patients with pancreatogenic hyperinsulinaemic hypoglycaemia. A large proportion of insulinomas express SSR2a, and a larger study is needed to fully assess the diagnostic accuracy of SR PET in patients with insulinoma and nesidioblastosis compared with current localizing studies used in clinical practice.

Risk factors for aggressive nonfunctional pancreatic neuroendocrine tumors and the role of endoscopic ultrasound guided fine-needle aspiration

Background:

Nonfunctional pancreatic neuroendocrine tumors (NF-pNETs) are increasingly being diagnosed but management, especially of small tumors, remains a clinical dilemma. Endoscopic ultrasound guided fine-needle aspiration (EUS-FNA) is now routinely used for diagnosis of pancreatic neuroendocrine tumors (pNETs) but has not been well studied as a tool for identifying aggressive disease.

Materials and Methods:

A systematic search of the cytology database identified all patients at our center who underwent EUS-FNA from 1999 through 2011 and were diagnosed with NF-pNET.

Results:

A total of 50 patients were identified. Though patients with metastatic disease had a mean tumor size of 40 mm compared to 25 mm in patients without metastatic disease (P = 0.04), we also identified several patients with tumors <20 mm who presented with metastatic disease. Furthermore, we found no statistically significant difference in metastatic disease between tumors <20 mm and >20 mm (P = 0.13). Using receiver operating characteristic (ROC) analysis, we found that using a cutoff point of 20 mm only led to a sensitivity of 85% in screening for metastases, while lowering the cutoff point to 18 mm allowed for a sensitivity of 95%.

Conclusion:

Currently, guidelines suggest that only patients with tumors greater than 20 mm undergo surgical resection, as tumors less than this size are thought to have low risk of metastases. Our analysis suggests that these recommendations could lead to undertreating patients with small tumors. Tumor size alone may be inadequate as a marker for aggressive NF-pNETs. Given this, other risk factors for aggressive pNETs should be studied to help identify the patients most likely to benefit from surgery.

Isoattenuating insulinomas at biphasic contrast-enhanced CT: frequency, clinicopathologic features and perfusion characteristics

OBJECTIVES

We aimed to determine the frequency of isoattenuating insulinomas, to investigate their clinicopathological features and to assess their regional pancreatic perfusion characteristics.

METHODS

Institutional review board approval was obtained, and patient informed consent was waived. From July 2010 to June 2014, 170 patients (66 male, 104 female) with endogenous hyperinsulinemic hypoglycemia underwent biphasic contrast-enhanced CT before surgery, and 129 of those patients also received preoperative whole-pancreas CT perfusion. A total of 181 tumours were proved histopathologically after surgery. Enhancement pattern and regional pancreatic perfusion characteristics were analyzed. Clinical features, tumour size and pathological grading were investigated.

RESULTS

The frequency of isoattenuating tumours was 24.9 %. Tumour size and WHO grading was not significantly different between isoattenuating and hyperattenuating tumours. Tumour-free regions had identical blood flow (BF) regardless of their location (p = 0.35). Isoattenuating tumour-harbouring regions had lower BF compared with hyperattenuating tumour-harbouring regions; both showed higher BF compared with tumour-free neighbourhood regions (all p < 0.01). For patients with isoattenuating tumours, the overall hospital stay was longer (p < 0.01).

CONCLUSIONS

A substantial subset of insulinomas were isoattenuating on biphasic CT. CT perfusion showed higher BF in tumour-harbouring regions compared to tumour-free regions, providing a clue for tumour regionalization.

KEY POINTS

• About a quarter of all insulinomas were isoattenuating on biphasic contrast-enhanced CT. • CT perfusion finds tumour-harbouring regions have higher blood-flow compared to tumour-free regions. • CT perfusion provides important information for tumour regionalization, for isoattenuating tumours.