Angiography and arterial stimulation venous sampling in the localization of pancreatic neuroendocrine tumours

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.

Essentials of Insulinoma Localization with Selective Arterial Calcium Stimulation and Hepatic Venous Sampling

Insulinomas are the most common functional pancreatic neuroendocrine tumor. Most insulinomas can be localized non-invasively with cross-sectional and nuclear imaging. Selective arterial calcium stimulation and hepatic venous sampling is an effective and safe minimally-invasive procedure for insulinoma localization that may be utilized when non-invasive techniques are inconclusive. The procedure’s technical success and proper interpretation of its results is dependent on the interventional radiologist’s knowledge of normal and variant pancreatic arterial perfusion. Accurate pre-operative localization aids in successful surgical resection. Technical and anatomic considerations of insulinoma localization with selective arterial calcium stimulation and hepatic venous sampling are reviewed.

Clinical Management of Malignant Insulinoma: a single Institution's experience over three decades

BACKGROUND

Malignant insulinoma is extremely rare and accounts for only 10% of total insulinoma cases. The goal of this study is to retrospectively analyze clinical data from 15 patients with malignant insulinoma treated at Peking Union Medical College Hospital (PUMCH) from 1984 to April 2017.

METHODS

"Malignant insulinoma" was used as the keywords in the PUMCH medical record retrieval system to search and obtain patients' clinical information. We identified subjects diagnosed with malignant insulinoma based on clinical or surgical pathological signs and subsequently analyzed their clinical data.

RESULTS

Eight males and seven females with a median age at diagnosis of 40 years (38-54 years) were included. Eight patients (53%) had developed metastases at diagnosis, while the others (46.67%) developed metastases during the follow-up visits. The major sites of metastasis were the liver (86.7%), local tissues and blood vessels (33%) and abdominal lymph nodes (13%). All patients displayed neuroglycopenic (100%) and/or autonomic (60%) symptoms, mostly during fasting periods (73.3%), with an average blood glucose level of 1.66 ± 0.51 mmol/L. A total of 93% of the patients had one primary pancreatic lesion, 53% had a lesion in the head of the pancreas, and 47% had a lesion in the tail of the pancreas, with diameters ranging between 0.9 and 6.0 cm. Most liver metastases were multiple lesions. Selective celiac arteriography yielded 100% sensitivity for both primary pancreatic lesions and liver metastases. Most patients received synthetical treatments, including surgery, chemoembolization, and octreotide.

CONCLUSIONS

Malignant insulinomas have a similar diagnostic process to that of benign insulinomas but require far more comprehensive therapies to alleviate hypoglycemic symptoms and extend patients' survival.

Pancreatic neuroendocrine tumors: contemporary diagnosis and management

Pancreatic neuroendocrine tumors (PNETs) are neoplasms that arise from the hormone producing cells of the islets of Langerhans, also known as pancreatic islet cells. PNETs are considered a subgroup of neuroendocrine tumors, and have unique biology, natural history and clinical management. These tumors are classified as 'functional' or 'non-functional' depending on whether they release peptide hormones that produce specific hormone- related symptoms, usually in established patterns based on tumor subtype. This manuscript will review pancreatic neuroendocrine tumor subtypes, syndromes, diagnosis, and clinical management.

Pancreatic insulinomas: Laparoscopic management

Insulinomas are rare pancreatic neuroendocrine tumors that are most commonly benign, solitary, and intrapancreatic. Uncontrolled insulin overproduction from the tumor produces neurological and adrenergic symptoms of hypoglycemia. Biochemical diagnosis is confirmed by the presence of Whipple’s triad, along with corroborating measurements of blood glucose, insulin, proinsulin, C-peptide, β-hydroxybutyrate, and negative tests for hypoglycemic agents during a supervised fasting period. This is accompanied by accurate preoperative localization using both invasive and non-invasive imaging modalities. Following this, careful preoperative planning is required, with the ensuing procedure being preferably carried out laparoscopically. An integral part of the laparoscopic approach is the application of laparoscopic intraoperative ultrasound, which is indispensable for accurate intraoperative localization of the lesion in the pancreatic region. The extent of laparoscopic resection is dependent on preoperative and intraoperative findings, but most commonly involves tumor enucleation or distal pancreatectomy. When performed in an experienced surgical unit, laparoscopic resection is associated with minimal mortality and excellent long-term cure rates. Furthermore, this approach confers equivalent safety and efficacy rates to open resection, while improving cosmesis and reducing hospital stay. As such, laparoscopic resection should be considered in all cases of benign insulinoma where adequate surgical expertise is available.

Clinical Presentation and Diagnosis of Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are slow-growing neoplasms capable of storing and secreting different peptides and neuroamines. Some of these substances cause specific symptom complexes, whereas others are silent. They usually have episodic expression, and the diagnosis is often made at a late stage. Although considered rare, the incidence of NETs is increasing. For these reasons, a high index of suspicion is needed. In this article, the different clinical syndromes and the pathophysiology of each tumor as well as the new and emerging biochemical markers and imaging techniques that should be used to facilitate an early diagnosis, follow-up, and prognosis are reviewed.

Intra-arterial calcium stimulation test with hepatic venous sampling for preoperative diagnosis of a large insulinoma in an obese young man

Herein, we report the case of a large benign insulinoma in an obese young man with a three-year history of asymptomatic hypoglycaemia. He presented to our outpatient department with a two-week history of dizziness and morning cold sweats. A random serum glucose test revealed hypoglycaemia. Upon admission, computed tomography and magnetic resonance imaging of the abdomen with intravenous contrast media showed an enhancing mass lesion in the uncinate process of the pancreas. To confirm the diagnosis, an intra-arterial calcium stimulation test with hepatic venous sampling was performed for preoperative localisation and to exclude the presence of occult insulinomas. The patient underwent an exploratory laparotomy, with successful resection of the pancreatic head tumour. Histology confirmed the diagnosis of insulinoma. The patient's postoperative recovery was uneventful, and he has not developed further episodes of hypoglycaemia three years post surgery.

GEP-NETS update: functional localisation and scintigraphy in neuroendocrine tumours of the gastrointestinal tract and pancreas (GEP-NETs)

For patients with neuroendocrine tumours (NETs) of the gastrointestinal tract and pancreas (GEP) (GEP-NETs), excellent care should ideally be provided by a multidisciplinary team of skilled health care professionals. In these patients, a combination of nuclear medicine imaging and conventional radiological imaging techniques is usually mandatory for primary tumour visualisation, tumour staging and evaluation of treatment. In specific cases, as in patients with occult insulinomas, sampling procedures can provide a clue as to where to localise the insulin-hypersecreting pancreatic NETs. Recent developments in these fields have led to an increase in the detection rate of primary GEP-NETs and their metastatic deposits. Radiopharmaceuticals targeted at specific tumour cell properties and processes can be used to provide sensitive and specific whole-body imaging. Functional imaging also allows for patient selection for receptor-based therapies and prediction of the efficacy of such therapies. Positron emission tomography/computed tomography (CT) and single-photon emission CT/CT are used to map functional images with anatomical localisations. As a result, tumour imaging and tumour follow-up strategies can be optimised for every individual GEP-NET patient. In some cases, functional imaging might give indications with regard to future tumour behaviour and prognosis.

The surgical management of insulinomas in children

PURPOSE

Insulinomas are rare pediatric tumors for which optimal localization studies and management remain undetermined. We present our experience with surgical management of insulinomas during childhood.

METHODS

A retrospective review was performed of patients who underwent surgical management for an insulinoma from 1999 to 2012.

RESULTS

The study included eight patients. Preoperative localization was successful with abdominal ultrasound, abdominal CT, endoscopic ultrasound, or MRI in only 20%, 28.6%, 40%, and 50% of patients, respectively. Octreotide scan was non-diagnostic in 4 patients. For diagnostic failure, selective utilization of 18-Fluoro-DOPA PET/CT scanning, arterial stimulation/venous sampling, or transhepatic portal venous sampling were successful in insulinoma localization. Intraoperatively, all lesions were identified by palpation or with the assistance of intraoperative ultrasound. Surgical resection using pancreas sparing techniques (enucleation or distal pancreatectomy) resulted in a cure in all patients. Postoperative complications included a pancreatic fistula in two patients and an additional missed insulinoma in a patient with MEN-1 requiring successful reoperation.

CONCLUSIONS

Preoperative tumor localization may require many imaging modalities to avoid unsuccessful blind pancreatectomy. Intraoperative palpation with the assistance of ultrasound offers a reliable method to precisely locate the insulinoma. Complete surgical resection results in a cure. Recurrent symptoms warrant evaluation for additional lesions.

Diagnosis and management of insulinoma

Insulinomas, the most common cause of hypoglycemia related to endogenous hyperinsulinism, occur in 1-4 people per million of the general population. Common autonomic symptoms of insulinoma include diaphroresis, tremor, and palpitations, whereas neuroglycopenenic symptoms include confusion, behavioural changes, personality changes, visual disturbances, seizure, and coma. Diagnosis of suspected cases is based on standard endocrine tests, especially the prolonged fasting test. Non-invasive imaging procedures, such as computed tomography and magnetic resonance imaging, are used when a diagnosis of insulinoma has been made to localize the source of pathological insulin secretion. Invasive modalities, such as endoscopic ultrasonography and arterial stimulation venous sampling, are highly accurate in the preoperative localization of insulinomas and have frequently been shown to be superior to non-invasive localization techniques. The range of techniques available for the localization of insulinomas means that blind resection can be avoided. Intraoperative manual palpation of the pancreas by an experienced surgeon and intraoperative ultrasonography are both sensitive methods with which to finalize the location of insulinomas. A high proportion of patients with insulinomas can be cured with surgery. In patients with malignant insulinomas, an aggressive medical approach, including extended pancreatic resection, liver resection, liver transplantation, chemoembolization, or radiofrequency ablation, is recommended to improve both survival and quality of life. In patients with unresectable or uncontrollable insulinomas, such as malignant insulinoma of the pancreas, several techniques should be considered, including administration of ocreotide and/or continuous glucose monitoring, to prevent hypoglycemic episodes and to improve quality of life.

[Endogenous hyperinsulinism: review and follow-up of 24 cases]

Hypoglycemia due to endogenous hyperinsulinism (EH) is diagnosed in a symptomatic patient with low levels of plasma glucose concomitant with elevated plasma insulin and C-peptide. Causes of EH are pancreatic islet-cells disease, use of insulin secretagogues, and autoimmune hypoglycemia. In this review, the authors studied 24 patients with hypoglycemia due to endogenous hyperinsulinism in order to describe aspects of diagnosis and treatment. Our study demonstrated that after 12 hours of fasting (mini-fasting test; at least three samples), all patients presented the diagnostic criteria for EH. Additionally, we found that 11 of 12 patients (91.7%) who underwent glucagon test achieved glucose levels less than 50 mg/dL and below baseline after 120 minutes. Mini-fasting (3 samples) and glucagon test may be useful to prevent prolonged fasting test to clarify the diagnosis of endogenous hyperinsulinism.

PET of insulinoma using ¹⁸F-FBEM-EM3106B, a new GLP-1 analogue

Derived from endocrine pancreatic beta cells, insulinomas express glucagon-like peptide-1 (GLP-1) receptor with high density and incidence. In this study, we labeled a novel GLP-1 analogue, EM3106B, with (18)F and performed PET imaging to visualize insulinoma tumors in an animal model. A GLP-1 analogue that contains multiple lactam bridges, EM3106B, was labeled with (18)F through a maleimide-based prosthetic group, N-2-(4-(18)F-fluorobenzamido)ethylmaleimide ((18)F-FBEM). The newly developed radiotracer was characterized by cell based receptor-binding assay, cell uptake and efflux assay. The stability in serum was evaluated by radio-HPLC analysis. In vivo PET imaging was performed in nude mice bearing subcutaneous INS-1 insulinoma tumors and MDA-MB-435 tumors of melanoma origin. Ex vivo biodistribution study was performed to confirm the PET imaging data. EM3106B showed high binding affinity (IC(50) = 1.38 nM) and high cell uptake (5.25 ± 0.61% after 120 min incubation). (18)F-FBEM conjugation of EM3106B resulted in high labeling yield (24.9 ± 2.4%) and high specific activity (>75 GBq/μmol at the end of bombardment). EM3106B specifically bound and was internalized by GLP-1R positive INS-1 cells. After intravenous injection of 3.7 MBq (100 μCi) of (18)F-FBEM-EM3106B, the INS-1 tumors were clearly visible with high contrast in relation to the contralateral background on PET images, and tumor uptake of (18)F-FBEM-EM3106B was determined to be 28.5 ± 4.7 and 25.4 ± 4.1% ID/g at 60 and 120 min, respectively. (18)F-FBEM-EM3106B showed low uptake in MB-MDA-435 tumors with low level of GLP-1R expression. Direct tissue sampling biodistribution experiment confirmed high tracer uptake in INS-1 tumors and receptor specificity in both INS-1 tumor and pancreas. In conclusion, (18)F-FBEM-EM3106B exhibited GLP-1R-receptor-specific targeting properties in insulinomas. The favorable characteristics of (18)F-FBEM-EM3106B, such as high specific activity and high tumor uptake, and high tumor to nontarget uptake, demonstrate that it is a promising tracer for clinical insulinoma imaging.

The role of interventional venous sampling in localising neuroendocrine tumours

PURPOSE OF REVIEW

This review focuses on the role of interventional venous sampling in the diagnosis and localization of neuroendocrine tumours (NETs), and its role in relation to conventional and novel imaging techniques.

RECENT FINDINGS

Imaging of NETs has evolved together with advances in imaging technology. Imaging localization plays an important role in the subsequent management of these tumours. This article provides an overview of the application of venous sampling in the localization of NETs, presented with current evidence to support its continued role in the diagnostic work-up of pituitary, parathyroid, pancreatic, adrenal and ovarian endocrine disease.

SUMMARY

Interventional venous sampling continues to be a highly sensitive modality in the localization of NETs. Although significant advances in noninvasive anatomic and functional imaging modalities have reduced the reliance of this well established technique, the latest literature continues to support its important role in the diagnostic armament of these unique and rare tumours.

Successful laparoscope resection of ectopic insulinoma in duodenohepatic ligament

Both ectopic pancreas and insulinoma are rare. A 21-year-old male patient had suffered from hypoglycemia episodes for 3 years and was diagnosed to have insulinoma based on biochemical and endocrinological evaluations. Various localization approaches revealed a distinct tumor outside the pancreas. With intraoperative endoscopy, the tumor in duodenohepatic ligament was identified and successfully resected. Pathologic evaluation revealed an ectopic insulinoma with ectopic pancreas. Therefore, when the biochemically confirmed insulinoma could not be well-definitely localized, the possibility of ectopic insulinoma should be suspected. In addition, radiography examinations and operation exploration should extend to the field where ectopic pancreas usually presents.

New and emerging syndromes due to neuroendocrine tumors

Neuroendocrine tumors (NETs) are rare, slow-growing neoplasms characterized by their ability to store and secrete different peptides and neuroamines. Some of these substances cause specific clinical syndromes whereas others are not associated with specific syndromes or symptom complexes. NETs usually have episodic expression that makes diagnosis difficult, erroneous, and often late. For these reasons a high index of suspicion is needed, and it is important to understand the pathophysiology of each tumor to decide which biochemical markers are more useful and when they should be used.

Pancreatic endocrine tumors

Pancreatic endocrine tumors have been steadily growing in incidence and prevalence during the last two decades, showing an incidence of 4-5/1,000,000 population. They represent a heterogeneous group with very varying tumor biology and prognosis. About half of the patients present clinical symptoms and syndromes related to substances released from the tumors (Zollinger-Ellison syndrome, insulinoma, glucagonoma, etc) and the other half are so-called nonfunctioning tumors mainly presenting with symptoms such as obstruction, jaundice, bleeding, and abdominal mass. Ten percent to 15% of the pancreatic endocrine tumors are part of an inherited syndrome such as multiple endocrine neoplasia type 1 (MEN-1), von Hippel-Lindau (VHL), neurofibromatosis, or tuberousclerosis. The diagnosis is based on histopathology demonstrating neuroendocrine features such as positive staining for chromogranin A and specific hormones such as gastrin, proinsulin, and glucagon. Moreover, the biochemical diagnosis includes measurement of chromogranins A and B or specific hormones such as gastrin, insulin, glucagon, and vasoactive intestinal polypeptide (VIP) in the circulation. In addition to standard localization procedures, radiology (computed tomography [CT] scan, magnetic resonance imaging [MRI], ultrasound [US]), somatostatin receptor scintigraphy, and most recently positron emission tomography with specific isotopes such as (11)C-5 hydroxytryptamin ((11)C-5-HTP), fluorodopa and (68)Ga-1,4,7,10-tetra-azacyclododecane-N,N',N″,N‴-tetra-acetic acid (DOTA)-octreotate are performed. Surgery is still one of the cornerstones in the management of pancreatic endocrine tumors, but curative surgery is rarely obtained in most cases because of metastatic disease. Debulking and other cytoreductive procedures might facilitate systemic treatment. Cytotoxic drugs, biological agents, such as somatostatin analogs, alpha interferons, mammalian target of rapamycin (mTOR) inhibitors and tyrosine kinase inhibitors are routinely used. Tumor-targeted radioactive treatment is available in many centres in Europe and is effective in patients with tumors that express high content of somatostatin receptors type 2 and 5. In the future, treatment will be based on tumor biology and molecular genetics with the aim of so-called personalized medicine.

NANETS treatment guidelines: well-differentiated neuroendocrine tumors of the stomach and pancreas

Well-differentiated neuroendocrine tumors (NETs) of the stomach and pancreas represent 2 major subtypes of gastrointestinal NETs. Historically, there has been little consensus on the classification and management of patients with these tumor subtypes. We provide an overview of well-differentiated NETs of the stomach and pancreas and describe consensus guidelines for the treatment of patients with these malignancies.

68Ga-labelled exendin-3, a new agent for the detection of insulinomas with PET

Purpose

Insulinomas are neuroendocrine tumours derived from pancreatic β-cells. The glucagon-like peptide 1 receptor (GLP-1R) is expressed with a high incidence (>90%) and high density in insulinomas. Glucagon-like peptide 1 (GLP-1), the natural ligand of GLP-1R, is rapidly degraded in vivo. A more stable agonist of GLP-1R is exendin-3. We investigated imaging of insulinomas with DOTA-conjugated exendin-3 labelled with ⁶⁸Ga.

Methods

Targeting of insulinomas with [Lys⁴⁰(DOTA)]exendin-3 labelled with either ¹¹¹In or ⁶⁸Ga was investigated in vitro using insulinoma tumour cells (INS-1). [Lys⁴⁰(¹¹¹In-DTPA)]Exendin-3 was used as a reference in this study. In vivo targeting was investigated in BALB/c nude mice with subcutaneous INS-1 tumours. PET imaging was performed using a preclinical PET/CT scanner.

Results

In vitro exendin-3 specifically bound and was internalized by GLP-1R-positive cells. In BALB/c nude mice with subcutaneous INS-1 tumours a high uptake of [Lys⁴⁰(¹¹¹In-DTPA)]exendin-3 in the tumour was observed (33.5 ± 11.6%ID/g at 4 h after injection). Uptake was specific, as determined by coinjection of an excess of unlabelled [Lys⁴⁰]exendin-3 (1.8 ± 0.1%ID/g). The pancreas also exhibited high and specific uptake (11.3 ± 1.0%ID/g). High uptake was also found in the kidneys (144 ± 24%ID/g) and this uptake was not receptor-mediated. In this murine tumour model optimal targeting of the GLP-1R expressing tumour was obtained at exendin doses ≤0.1 µg. Remarkably, tumour uptake of ⁶⁸Ga-labelled [Lys⁴⁰(DOTA)]exendin-3 was lower (8.9 ± 3.1%ID/g) than tumour uptake of ¹¹¹In-labelled [Lys⁴⁰(DTPA)]exendin-3 (25.4 ± 7.2%ID/g). The subcutaneous tumours were clearly visualized by small-animal PET imaging after injection of 3 MBq of [Lys⁴⁰(⁶⁸Ga-DOTA)]exendin-3.

Conclusion

[Lys⁴⁰(⁶⁸Ga-DOTA)]Exendin-3 specifically accumulates in insulinomas, although the uptake is lower than that of [Lys⁴⁰(¹¹¹In-DTPA)]exendin-3. Therefore, [Lys⁴⁰(⁶⁸Ga-DOTA)]exendin-3 is a promising tracer to visualize insulinomas with PET.

[Hypoglycemia and insulinoma]

Insulinomas are rare causes of hypoglycemia. After having ruled out non insulinomatous causes of hypoglycemia in a patient in whom Whipple's triad is documented, hyperinsulinism must be demonstrated biochemically, either during a spontaneous hypoglycemic episode or, more often, during a supervised fast which may be prolonged up to 72 h. A mixed-meal test may also help to diagnose the very rare cases of postprandial hypoglycemia related to non insulinoma pancreatogenic hypoglycemic syndrome (NIPHS) or to some rare insulinomas. Only when diagnosis of hypoglycemic hyperinsulinism is made, the tumor localization process may be initiated. This may be difficult due to the small size of insulinomas (generally < 1 cm). Multimodal approach is necessary. The association of endoscopic ultrasound and CT-scan or MRI seems optimal. Octreoscan will be also performed. First results with a very new technique, the GLP-1 receptor imaging, are promising for localizing very small tumors. This localization aims to allow a sparing surgery; enucleation of benign tumors, if possible, allows a pancreatic tissue preservation in patients with quite normal survival.

The role of arterial stimulation and simultaneous venous sampling in addition to cross-sectional imaging for localisation of biochemically proven insulinoma

Insulinomas, although rare, cause considerable morbidity but are frequently amenable to surgical cure. Laparoscopic surgery can now be considered if the tumour is localised pre-operatively, but the optimal imaging approach has not been determined. The objective of this study was to evaluate the ability of different imaging investigations, including CT, MRI, endoscopic ultrasound, octreotide scintigraphy and arterial stimulation with simultaneous venous sampling (ASVS), to localise insulinomas. All patients with biochemically proven insulinoma at our institution underwent ASVS along with other imaging investigations as part of their routine investigation. The results of these investigations were compared with histological findings. Twenty-eight patients with biochemically proven insulinoma confirmed by histology were identified. Ultimately ASVS localised a lesion in all patients. Seventeen patients (61%) had laparoscopic surgery. Tumor-detection rates for other imaging investigations included 43.5% of cases using CT, 71% using MRI, 86% using endoscopic ultrasound and 33% using octreotide scintigraphy. In four patients, the ASVS was the only test to correctly localise the lesion. ASVS should be considered routinely before surgery to ensure accurate localisation of insulinomas.

[Invasive diagnostic procedures for insulinomas of the pancreas]

Insulinomas are the most common cause for hypoglycemia with endogenous hyperinsulinism. Insulinomas are the most frequent endocrine tumor of the pancreas and 10% occur as multiple tumors (e.g. multiple endocrine neoplasia type I) or in rare cases as islet cell hyperplasia. A further 10-15% of insulinomas are malignant. Non-invasive imaging modalities, such as computed tomography (CT), magnetic resonance imaging (MRI), ultrasonography (US) and somatoreceptor scintigraphy (SRN) show a lower sensitivity for detection and localization of tumors, because in many cases insulinomas are smaller than 2 cm in size. Invasive pre-operative diagnostic procedures, such as transhepatic peripancreatic venous blood sampling (TPVB) and the intra-arterial calcium stimulation test (ASVS) are much more time-intensive compared to CT, MRI and US with an examination time of 2-3 h but achieve a more exact pre-operative detection and localization with sensitivities mostly greater than 95% and are therefore the diagnostic methods of choice.

Neuroendocrine tumors of the pancreas

This literature review briefly summarizes the epidemiology, pathophysiology, clinical management, and outcomes of patients with pancreatic neuroendocrine tumors (PNETs) and highlights recent advances in PNET research. PNETs are rare neoplasms, compared with carcinomas arising from pancreatic exocrine tissue. They, like other neuroendocrine tumor types, display variable malignant potential, hormone-related syndromes (functionality), localization, and genetic background. Although tumor origin and molecular pathogenesis remain poorly understood, recently established grading and staging systems facilitate patient risk stratification, and thereby directly impact clinical decision making. Although the optimal clinical management of PNETs involves a multidisciplinary approach, surgery remains the only curative treatment for early-stage disease. Surgery may also have a role in patients with advanced-stage disease, including those with hepatic metastases. Alternative therapeutic approaches applied to PNETs, including chemotherapy, radiofrequency ablation, transarterial chemoembolization, biotherapy, polypeptide radionuclide receptor therapy, antiangiogenic therapy, and selective internal radiotherapy, have failed to demonstrate a long-term survival benefit. Surgery remains the primary therapeutic option for patients with PNETs. Research on PNETs is desperately needed to improve the therapeutic options for patients with this disease.

Evaluation and management of adult hypoglycemic disorders: an Endocrine Society Clinical Practice Guideline

OBJECTIVE

The aim is to provide guidelines for the evaluation and management of adults with hypoglycemic disorders, including those with diabetes mellitus.

EVIDENCE

Using the recommendations of the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system, the quality of evidence is graded very low (plus sign in circle ooo), low (plus sign in circle plus sign in circle oo), moderate (plus sign in circle plus sign in circle plus sign in circle o), or high (plus sign in circle plus sign in circle plus sign in circle plus sign in circle).

CONCLUSIONS

We recommend evaluation and management of hypoglycemia only in patients in whom Whipple's triad--symptoms, signs, or both consistent with hypoglycemia, a low plasma glucose concentration, and resolution of those symptoms or signs after the plasma glucose concentration is raised--is documented. In patients with hypoglycemia without diabetes mellitus, we recommend the following strategy. First, pursue clinical clues to potential hypoglycemic etiologies--drugs, critical illnesses, hormone deficiencies, nonislet cell tumors. In the absence of these causes, the differential diagnosis narrows to accidental, surreptitious, or even malicious hypoglycemia or endogenous hyperinsulinism. In patients suspected of having endogenous hyperinsulinism, measure plasma glucose, insulin, C-peptide, proinsulin, beta-hydroxybutyrate, and circulating oral hypoglycemic agents during an episode of hypoglycemia and measure insulin antibodies. Insulin or insulin secretagogue treatment of diabetes mellitus is the most common cause of hypoglycemia. We recommend the practice of hypoglycemia risk factor reduction--addressing the issue of hypoglycemia, applying the principles of intensive glycemic therapy, and considering both the conventional risk factors and those indicative of compromised defenses against falling plasma glucose concentrations--in persons with diabetes.

Gastrointestinal neuroendocrine tumors: pancreatic endocrine tumors

Pancreatic endocrine tumors (PETs) have long fascinated clinicians and investigators despite their relative rarity. Their clinical presentation varies depending on whether the tumor is functional or not, and also according to the specific hormonal syndrome produced. Tumors may be sporadic or inherited, but little is known about their molecular pathology, especially the sporadic forms. Chromogranin A appears to be the most useful serum marker for diagnosis, staging, and monitoring. Initially, therapy should be directed at the hormonal syndrome because this has the major initial impact on the patient's health. Most PETs are relatively indolent but ultimately malignant, except for insulinomas, which predominantly are benign. Surgery is the only modality that offers the possibility of cure, although it generally is noncurative in patients with Zollinger-Ellison syndrome or nonfunctional PETs with multiple endocrine neoplasia-type 1. Preoperative staging of disease extent is necessary to determine the likelihood of complete resection although debulking surgery often is believed to be useful in patients with unresectable tumors. Once metastatic, biotherapy is usually the first modality used because it generally is well tolerated. Systemic or regional therapies generally are reserved until symptoms occur or tumor growth is rapid. Recently, a number of newer agents, as well as receptor-directed radiotherapy, are being evaluated for patients with advanced disease. This review addresses a number of recent advances regarding the molecular pathology, diagnosis, localization, and management of PETs including discussion of peptide-receptor radionuclide therapy and other novel antitumor approaches. We conclude with a discussion of future directions and unsettled problems in the field.

Endocrine pancreatic tumors: diagnosis and treatment

Endocrine pancreatic tumors (EPTs) are uncommon, having an incidence of one per 100,000 people. They may appear as sporadic tumors or be associated with hereditary syndromes. EPTs are categorized as functioning or nonfunctioning tumors, based on the presence or absence of clinical syndromes. Among the former, insulinomas and gastrinomas are the most common. For the histopathological investigation of EPTs, chromogranin A and synaptophysin immunostainings are recommended. Measurement of circulating chromogranin A is also the cornerstone for the biochemical diagnosis of these tumors. Furthermore, specific hormones produced and released by the neoplastic cells can be identified by immunostaining and used for biochemical evaluation. To locate EPTs, both noninvasive (ultrasonography, computerized tomography, MRI and radionuclear imaging) and invasive techniques (arterial stimulation with venous sampling) can be used. Debulking procedures (surgery, radiofrequency ablation, embolization/chemoembolization and liver transplantation) and/or medical treatment (chemotherapy, biotherapy and peptide receptor radionuclide therapy) are the options available for the treatment of EPTs. Understanding the molecular events underlying the pathobiology of EPTs will aid the development of more accurate diagnostic/prognostic markers and give guidance for improved therapeutic modalities.

Occult sporadic insulinoma: Localization and surgical strategy

Insulinomas continue to pose a diagnostic challenge to physicians, surgeons and radiologists alike. Most are intrapancreatic, benign and solitary. Biochemical diagnosis is obtained and imaging techniques to localize lesions continue to evolve. Surgical resection is the treatment of choice. Despite all efforts, an occult insulinoma (occult insulinoma refers to a biochemically proven tumor with indeterminate anatomical site before operation) may still be encountered. New localization preoperative techniques decreases occult cases and the knowledge of the site of the mass before surgery allows to determine whether enucleation of the tumor or pancreatic resection is likely to be required and whether the tumor is amenable to removal via a laparoscopic approach. In absence of preoperative localization and intraoperative detection of an insulinoma, blind pancreatic resection is not recommended.

Insulinoma associated with pregnancy

OBJECTIVE

To report three cases of insulinoma associated with pregnancy.

DESIGN

Case report.

SETTING

Divisions of Endocrinology and Gastroenterologic Surgery, Hospital de Clínicas, University of Buenos Aires, Argentina.

PATIENT(S)

Three patients with hypoglycemic signs due to insulinoma appearing during pregnancy or shortly after delivery.

INTERVENTION(S)

Laparoscopic excision of insulinoma in two and laparotomy in one of the patients were performed after the end of their pregnancies.

MAIN OUTCOME MEASURE(S)

Disappearance of hypoglycemic crises and histologic proof of insulinomas.

RESULT(S)

In two of the three patients, hypoglycemia occurred within 2-12 weeks after delivery, suggesting that signs could have been masked because of metabolic changes during gestation; in the third patient, hypoglycemia appeared in the first trimester but was misinterpreted.

CONCLUSION(S)

Insulinoma is often not suspected during the first trimester of pregnancy because signs resemble episodes of hypotension or emesis. Later, with the increase in insulin resistance, symptoms subside.

The Current Role of Venous Sampling in the Localization of Endocrine Disease

Endocrine venous sampling plays a specific role in the diagnosis of endocrine disorders. In this article, we cover inferior petrosal sinus sampling, selective parathyroid venous sampling, hepatic venous sampling with arterial stimulation, adrenal venous sampling, and ovarian venous sampling. We review their indications and the scientific evidence justifying these indications in the diagnosis and management of Cushing's syndrome, hyperparathyroidism, pancreatic endocrine tumors, Conn's syndrome, primary hyperaldosteronism, pheochromocytomas, and androgen-secreting ovarian tumors. For each sampling technique, we compare its diagnostic accuracy with that of other imaging techniques and, where possible, look at how it impacts patient management. Finally, we incorporate venous sampling into diagnostic algorithms used at our institution.

Usefulness of F-18 FDG-PET in detection of multiple endocrine tumors with duodenal carcinoid

In a 76-year-old woman in whom hypercalcemia had been followed, whole body fluorodeoxyglucose positron emission tomography (FDG-PET) scan detected hypermetabolic areas in the left lower region of the thyroid gland, pancreas tail, and duodenum. CT, MR, biopsy, and surgery were performed and parathyroid adenoma, pancreatic gastrinoma, and duodenal carcinoid were diagnosed. Fluorine-18 (F-18) FDG-PET may be useful for diagnosis of multiple endocrine tumors with duodenal carcinoid.

Review article: Pathogenesis and management of gastric carcinoid tumours

BACKGROUND

Gastric carcinoid tumours are rare, but are increasing in incidence.

AIM

To discuss tumour pathogenesis and outline current approaches to patient management.

METHODS

Review of published articles following a Pubmed search.

RESULTS

Although interest in gastric carcinoids has increased since it was recognized that they are associated with achlorhydria, to date there is no definite evidence that humans taking long-term acid suppressing medication are at increased risk. Type I tumours are associated with autoimmune atrophic gastritis and hypergastrinaemia, type II are associated with Zollinger-Ellison syndrome, multiple endocrine neoplasia-1 and hypergastrinaemia and sporadic type III carcinoids are gastrin-independent and carry the worst prognosis. Careful investigation of these patients is required, particularly to identify the tumour type, the source of hypergastrinaemia and the presence of metastases. Treatment can be directed at the source of hypergastrinaemia if type I or II tumours are still gastrin responsive and not growing autonomously. Type III tumours should be treated surgically.

CONCLUSIONS

Advances in our understanding of the pathogenesis of gastric carcinoids have led to recent improvements in investigation and management. Challenges remain in identifying the genetic and environmental factors, in addition to hypergastrinaemia, that are responsible for tumour development in susceptible patients.