Pitfalls in endosonographic imaging of suspected insulinomas: pancreatic nodules of unknown dignity

Relevance of Endoscopic Ultrasound in Endocrinology Today: Multiple Endocrine Neoplasia Type 1, Insulinoma, Primary Aldosteronism-An Expert's Perspective Based on Three Decades of Scientific and Clinical Experience

In endocrinology, endoscopic ultrasound (EUS) may be used to image the adrenals, the endocrine pancreas, and other organs where endocrine neoplasms may occur. During the recent decades, EUS has been established predominantly to assess multiple endocrine neoplasia type 1, to localize insulinomas, and to identify aldosterone-producing adenomas. EUS in endocrinology requires special skills and individual experience in order to provide reliable diagnostic information.

Endogenous hyperinsulinism: diagnostic and therapeutic difficulties

Endogenous hyperinsulinism is an abnormal clinical condition that involves excessive insulin secretion, related in 55% of cases to insulinoma. Other causes are possible such as islet cell hyperplasia, nesidioblastosis or antibodies to insulin or to the insulin receptor. Differentiation between these diseases may be difficult despite the use of several morphological examinations. We report six patients operated on for endogenous hyperinsulinism from 1^st January 2000 to 31^st December 2015. Endogenous hyperinsulinism was caused by insulinoma in three cases, endocrine cells hyperplasia in two cases and no pathological lesions were found in the last case. All patients typically presented with adrenergic and neuroglycopenic symptoms with a low blood glucose level concomitant with high insulin and C-peptide levels. Computed tomography showed insulinoma in one case out of two. MRI was carried out four times and succeeded to locate the lesion in the two cases of insulinoma. Endoscopic ultrasound showed one insulinoma and provided false positive findings three times out of four. Intra operative ultrasound succeeded to localize the insulinoma in two cases but was false positive in two cases. Procedures were one duodenopancreatectomy, two left splenopancreatectomy and two enucleations. For the sixth case, no lesion was radiologically objectified. Hence, a left blind pancreatectomy was practised but the pathological examination showed normal pancreatic tissue. Our work showed that even if morphological examinations are suggestive of insulinoma, other causes of endogenous hyperinsulinism must be considered and therefore invasive explorations should be carried out.

An update on the management of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are a rare and heterogeneous group of neoplasia and differ in their clinical presentation, behavior, and prognosis based on both histological features and cancer stage at the time of diagnosis. Although small-sized tumors can be surgically resected, locally advanced and metastatic tumors confer a poor prognosis. In addition, only limited treatment options are available to the latter group of patients with PNETs, such as hormonal analogs, cytotoxic agents, and targeted therapy. In selected patients, liver-directed therapies are also used. As expected, clinicians taking care of these patients are challenged to develop an effective and comprehensive treatment strategy for their patients amid a wide variety of treatment modalities. Targeted therapy for PNETs is limited to sunitinib and everolimus. Presently, a number of clinical studies are ongoing to assess the efficacy of newer targeted agents alone and in combination with previous agents for the treatment of advanced PNETs. The authors reviewed the current treatment and also discussed the emerging agents and emphasized the need to identify biomarkers.

Preoperative Imaging Overestimates the Tumor Size in Pancreatic Neuroendocrine Neoplasms Associated with Multiple Endocrine Neoplasia Type 1

BACKGROUND

Radiological tumor size of non-functioning pancreatic neuroendocrine neoplasms (Nf-pNENs) associated with multiple endocrine neoplasia type 1 (MEN1) is a crucial parameter to indicate surgery. The aim of this study was to compare radiological size (RS) and pathologic size (PS) of MEN1 associated with pNENs.

METHODS

Prospectively collected data of MEN1 patients who underwent pancreatic resections for pNENs were retrospectively analyzed. RS was defined as the largest tumor diameter measured on endoscopic ultrasound (EUS), magnetic resonance imaging (MRI) or computed tomography (CT). PS was defined as the largest tumor diameter on pathological analysis. Student's t test and linear regression analysis were used to compare the median RS and PS. p < 0.05 was considered significant.

RESULTS

Forty-four patients with a median age of 37 (range 10-68) years underwent primary pancreatic resections for pNENs. Overall, the median RS (20 mm, range 3-100 mm) was significantly larger than the PS (13 mm, range 4-110 mm) (p = 0.001). In patients with pNENs < 20 mm (n = 27), the size difference (median RS 15 mm vs PS 12 mm) was also significant (p = 0.003). However, the only modality that significantly overestimated the PS was EUS (median RS 14 mm vs 11 mm; p = 0.0002). RS overestimated the PS in 21 patients (21 of 27 patients, 78%). Five of 11 patients (12%) with a Nf-pNEN and a RS > 20 mm had in reality a PS < 20 mm. MRI was the imaging technique that best correlated with PS in the total cohort (r = 0.8; p < 0.0001), whereas EUS was the best correlating imaging tool in pNENs < 20 mm (r = 0.5; p = 0.0001).

CONCLUSION

Preoperative imaging, especially EUS, frequently overestimates the size of MEN1-pNENs, especially those with a PS < 20 mm. This should be considered when indicating surgery in MEN1 patients with small Nf-pNENs.

Management of neuroendocrine tumors of unknown primary

Neuroendocrine neoplams (NENs) are mostly relatively indolent malignancies but a significant number have metastatic disease at diagnosis mainly to the liver. Although in the majority of such cases the primary origin of the tumor can be identified, in approximately 11-22% no primary tumor is found and such cases are designated as NENs of unknown primary origin (UPO). This has significant therapeutic implications with respect to potentially resectable hepatic disease and/or application of appropriate medical therapy, either chemotherapeutic agents or targeted treatment, as the response to various treatments varies according to the origin of the primary tumor. This lack of tumor specific orientated treatment may also account for the relatively poorer prognosis of NENs of UPO compared to metastatic NENs with a known primary site. In the majority of cases the primary tumors are located in the small bowel and the lung, but a number may still elude detection. Occasionally the presence of a functional syndrome may direct to the specific tissue of origin but in the majority of cases a number of biochemical, imaging, histopathological and molecular modalities are utilized to help identify the primary origin of the tumor and direct treatment accordingly. Several diagnostic algorithms have recently been developed to help localize an occult primary tumor; however, in a number of cases no lesion is identified even after prolonged follow-up. It is expected that the delineation of the molecular signature of the different NENs may help identify such cases and provide appropriate treatment.

Endoscopic diagnosis and treatment of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are rare pancreatic neoplasms comprising only 1% to 2% of all pancreatic tumors. In recent years, the number of incidentally discovered PNETs has greatly increased given the widespread use of axial imaging. However, a significant proportion of PNETs may not be visualized on conventional imaging such as computed tomography, magnetic resonance imaging, and somatostatin receptor scintigraphy. Endoscopic ultrasound (EUS) has become an integral part of the diagnosis of PNETs because of its high sensitivity for detecting, localizing, and diagnosing PNETs. EUS-guided tissue acquisition provides histologic and immunologic confirmation, and may also allow prognostication about tumor behavior. In addition to preoperative assessment of these tumors, EUS has also been shown to have an important role in nonoperative management of small nonfunctional PNETs. Finally, recent developments suggest that interventional EUS may be used to aid intraoperative localization of PNETs and to deliver therapeutic agents for the treatment of PNETs. This review will discuss the endoscopic diagnosis and treatment of PNETs, with focus on recent advances in the utility of EUS in the clinical management of these tumors.

Endoscopic ultrasound in gastroenteropancreatic neuroendocrine tumors

Endoscopic ultrasound (EUS) is an advanced endoscopic technique currently used in the staging and diagnosis of many gastrointestinal neoplasms. The proximity of the echoendoscope to the gastrointestinal tract lends itself to a detailed view of the luminal pathology and the pancreas. This unique ability enables endoscopists to use EUS in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Diagnostic EUS allows previously unidentified NETs to be localized. EUS also determines tumor management by staging the GEP-NETS, enabling the clinicians to choose the appropriate endoscopic or surgical management. The ability to obtain a tissue diagnosis with EUS guidance enables disease confirmation. Finally, recent developments suggest that EUS may be used to deliver therapeutic agents for the treatment of NETs. This review will highlight the advances in our knowledge of EUS in the clinical management of these tumors.

Screening of pancreaticoduodenal endocrine tumours in patients with MEN 1: multidetector-row computed tomography vs. endoscopic ultrasound

PURPOSE

The authors compared multidetector-row computed tomography (MDCT) and endoscopic ultrasound (EUS) in the identification of pancreaticoduodenal endocrine tumours (PETs) in patients with multiple endocrine neoplasia type 1 (MEN 1).

MATERIALS AND METHODS

Fourteen consecutive patients (eight men and six women, aged 26-54 years) with MEN 1 underwent MDCT performed with a 4- (n=5) or 64- (n=9) detector-row system and EUS done with a radial transducer (7.5-20 MHz) within 7-28 days of each other. Prior to MDCT examination, patients were given 750 cc of water and asked to lie down in the right lateral decubitus for 15 min. Multiphase MDCT images were acquired both before and after the injection of nonionic iodinated contrast material (2 cc/kg) at an injection rate of 4 ml/s, with technical parameters and scan delay varying in relation to the system used. Images were all reconstructed at 3-mm intervals for the three phases (arterial, pancreatic and portal) and evaluated on a dedicated workstation.

RESULTS

MDCT detected a total of 25 PETs (3-18 mm) in nine patients. Of these lesions, nine were situated within the duodenal wall and 16 in either the pancreatic head (n=3), body (n=7), or tail (n=6). Three additional lesions were detected retrospectively after EUS imaging. Most (18/22, 81%) were hypervascular nodules, and four appeared as either hypoattenuating or cystic lesions. EUS detected a total of 32 PETs (2-18 mm) in 11 patients. Most lesions (29/32, 90%) appeared hypoechoic and were situated in the duodenal wall (n=15) or in either the pancreatic head (n=10), body (n=6) or tail (n=1).

CONCLUSIONS

Our preliminary data indicate that MDCT is complementary to EUS in the identification of PETs in MEN-1 patients.

Localization of insulinomas to regions of the pancreas by intraarterial calcium stimulation: the NIH experience

CONTEXT

Selective intraarterial calcium injection of the major pancreatic arteries with hepatic venous sampling [calcium arterial stimulation (CaStim)] has been used as a localizing tool for insulinomas at the National Institutes of Health (NIH) since 1989. The accuracy of this technique for localizing insulinomas was reported for all cases until 1996.

OBJECTIVES

The aim of the study was to assess the accuracy and track record of the CaStim over time and in the context of evolving technology and to review issues related to result interpretation and procedure complications. CaStim was the only invasive preoperative localization modality used at our center. Endoscopic ultrasound (US) was not studied.

DESIGN AND SETTING

We conducted a retrospective case review at a referral center.

PATIENTS

Twenty-nine women and 16 men (mean age, 47 yr; range, 13-78) were diagnosed with an insulinoma from 1996-2008.

INTERVENTION

A supervised fast was conducted to confirm the diagnosis of insulinoma. US, computed tomography (CT), magnetic resonance imaging (MRI), and CaStim were used as preoperative localization studies. Localization predicted by each preoperative test was compared to surgical localization for accuracy.

MAIN OUTCOME

We measured the accuracy of US, CT, MRI, and CaStim for localization of insulinomas preoperatively.

RESULTS

All 45 patients had surgically proven insulinomas. Thirty-eight of 45 (84%) localized to the correct anatomical region by CaStim. In five of 45 (11%) patients, the CaStim was falsely negative. Two of 45 (4%) had false-positive localizations.

CONCLUSION

The CaStim has remained vastly superior to abdominal US, CT, or MRI over time as a preoperative localizing tool for insulinomas. The utility of the CaStim for this purpose and in this setting is thus validated.

Neuroendocrine tumors of the pancreas: endoscopic diagnosis

PURPOSE OF REVIEW

Endoscopic ultrasound (EUS) is a valuable tool in the diagnosis and management of pancreatic neuroendocrine tumors. This review highlights advances over the last year in EUS in the evaluation of pancreatic neuroendocrine tumors.

RECENT FINDINGS

We will focus on recent findings regarding the accuracy of EUS, EUS-guided fine needle aspiration (EUS-fine needle aspiration), emerging cytologic markers obtained from fine needle aspiration samples, and the role of EUS screening for patients with multiple endocrine neoplasia type 1 syndrome. Additionally, we will introduce potential therapeutic EUS interventions in the treatment of pancreatic neuroendocrine tumors.

SUMMARY

The present review highlights recent advances in the utility of EUS in the clinical management of pancreatic neuroendocrine tumors. Key studies from the last year demonstrate the important role of EUS in the diagnosis, prognosis, and treatment of pancreatic neuroendocrine tumors.

Surgical aspects of gastrinoma in multiple endocrine neoplasia type 1

Gastrinoma is the most frequent functional pancreaticoduodenal endocrine tumor in patients with multiple endocrine neoplasia type 1 (MEN1) and one major determinant of mortality in this syndrome. Whether routine surgical exploration should be performed in a patient with MEN1 associated Zollinger-Ellison syndrome (ZES) to possibly reduce the malignant spread and eventually increase survival still remains controversial. There is not only disagreement about the indication for surgical exploration, but also what type of procedure should be performed, since sufficient evidence-based data are not available. The article discusses the available data on treatment strategies of MEN1 associated ZES.

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.

Preoperative diagnosis of insulinoma: low body mass index, young age, and female gender are associated with negative imaging by endoscopic ultrasound

OBJECTIVE

Endoscopic ultrasound (EUS) is a highly reliable procedure to localize insulinomas preoperatively. It has been considered to be important in planning surgical strategy, especially considering a minimal invasive approach. However, even under ideal conditions experienced examiners miss about 10-20% of insulinomas by EUS imaging.

DESIGN AND METHODS

This retrospective study aimed to identify factors associated with negative EUS imaging. Twenty-nine consecutive patients (24 benign and 5 malignant) with sporadic pancreatic insulinomas confirmed by successful surgery and positive histopathology were included. All EUS examinations were performed by one single experienced examiner over a period of one decade.

RESULTS

Three of the tumors were not detected by preoperative EUS as they were isoechoic to the surrounding healthy pancreatic tissue; 25 could be detected as hypoechoic lesions, (including all malignant tumors), and one lesion was hyperechoic. Low body mass index (P=0.053) and young age (P=0.037) were associated with negative EUS imaging. All patients with negative imaging were females. The position on the examiner's learning curve, the diameter and location of insulinoma, and endocrine parameters (insulin concentrations and insulin-glucose ratios in the prolonged fasting test) had no influence on the success of EUS imaging.

CONCLUSIONS

Some insulinomas are missed by preoperative EUS imaging as they are completely isoechoic. A low body mass index, female gender, and young age might be risk factors for negative imaging.

Hyperinsulinemic hypoglycemia due to adult nesidioblastosis in insulin-dependent diabetes

In neonates, persistent hyperinsulinemic hypoglycemia (PHH) is associated with nesidioblastosis. In adults, PHH is usually caused by solitary benign insulinomas. We report on an adult patient who suffered from insulin-dependent diabetes mellitus, and subsequently developed PHH caused by diffuse nesidioblastosis. Mutations of the MEN1 and Mody 2/3 genes were ruled out. Preoperative diagnostic procedures, the histopathological criteria and the surgical treatment options of adult nesidioblastosis are discussed. So far only one similar case of adult nesidioblastosis subsequent to diabetes mellitus II has been reported in the literature. In case of conversion of diabetes into hyperinsulinemic hypoglycemia syndrome, nesidioblastosis in addition to insulinoma should be considered.

Endoscopic ultrasound in the localisation of pancreatic islet cell tumours

The role of endoscopic ultrasound (EUS) in the evaluation of entero-pancreatic endocrine tumours has evolved in conjunction with advances in other imaging methods. The high spatial resolution of this technique allows the detection of very small lesions and their precise anatomical localisation. In patients with biochemically proven insulinoma, EUS can be effectively used as a first line investigation, with a sensitivity of 94%. Combined with thin section CT, the sensitivity rises to 100%. There is also high sensitivity in diagnosing intrapancreatic gastrinomas but lower for those arising in the duodenal wall which require detailed duodenal evaluation at surgery. EUS in conjunction with Somatostatin Receptor Scanning (SRS) has a combined sensitivity of 93% for gastrinomas. EUS is recommended for screening of asymptomatic patients with genetically proven MEN1. There is a limited role for EUS guided biopsy in pancreatic endocrine tumours.

Prospective evaluation of imaging procedures for the detection of pancreaticoduodenal endocrine tumors in patients with multiple endocrine neoplasia type 1

Early identification of pancreaticoduodenal endocrine tumors (PETs) in multiple endocrine neoplasia type 1 (MEN-1) is mandatory, because these tumors represent the most common cause of death within the syndrome. The diagnostic value of imaging procedures has therefore been evaluated in a prospective observational study. Between December 1997 and June 2003 twenty-two MEN-1 patients with genetically confirmed disease were followed for PETs using a standardized screening program with serum hormone measurements, endoscopic ultrasonography (EUS), computed tomography (CT), and somatostatin-receptor scintigraphy (SRS). Results could be validated by surgery and histopathology in 13 patients during 18 operations. In 12 asymptomatic patients with tumors measuring 10 mm or less, who have not yet undergone operation, PETs were detected by EUS in 12/12, by CT in 1/12, and by SRS in 2/11 cases. In 13 patients who have undergone surgical exploration EUS, CT, and SRS were true positive in 12 of 16, 7 of 13, and 12 of 17 cases, respectively, although the number of tumors detected by each imaging procedure alone was lower than the number detected intraoperatively and histopathologically in almost every case. A solitary liver metastasis in one patient and a nonfunctioning PET recurrence in another were identified only by SRS. Endoscopic ultrasonography is the most sensitive imaging procedure for the detection of small (< or = 10 mm) PETs in MEN-1, whereas SRS is the procedure of choice for the identification of metastases of MEN-1 PETs-i.e., for staging. Detection of PETs at an early stage by an aggressive screening program using EUS may lead to prompt surgical intervention and improved prognosis of MEN-1 PETs.

Resolved and unresolved controversies in the surgical management of patients with Zollinger-Ellison syndrome

OBJECTIVE

Highlight unresolved controversies in the management of Zollinger-Ellison syndrome (ZES).

SUMMARY BACKGROUND DATA

Recent studies have resolved some of the previous controversies including the surgical cure rate in patients with and without Multiple Endocrine Neoplasia-type1 (MEN1), the biological behavior of duodenal and pancreatic gastrinomas, role of imaging studies to localize tumor, and gastrectomy to manage acid output.

METHODS

Review of the literature based on computer searches in Index Medicus, Pubmed and Ovid.

RESULTS

Current controversies as identified in the literature include the role of endoscopic ultrasound (EUS), surgery in ZES patients with MEN1, pancreaticoduodenectomy (Whipple procedure), lymph node primary gastrinoma, parietal cell vagotomy, reoperation and surgery for metastatic tumor, and the use of minimally invasive surgical techniques to localize and remove gastrinoma.

CONCLUSIONS

It is hoped that future studies will focus on these issues to improve the surgical management of ZES patients.