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.

Ectopic insulinoma diagnosed by 68Ga-Exendin-4 PET/CT: A case report and review of literature

RATIONALE

Ectopic insulinomas are extremely rare and challenging to diagnose for clinicians. Precise preoperative localization is essential to successful treatment.

PATIENT CONCERNS

A 23-year-old man presented with a 1-year history of recurrent hypoglycemia.

DIAGNOSIS

Examinations in the local hospital did not reveal any pancreatic lesion. After admission, a fasting test and a 5-hour oral glucose tolerance test (OGTT) suggested a diagnosis of endogenous hyperinsulinemic hypoglycemia. Enhanced volume perfusion computed tomography (VPCT) revealed 2 nodules in the tail of the pancreas, a nodule in the gastric antrum, and a nodule in the hilum of the spleen. To differentiate which nodule was responsible for hypoglycemia, we performed 68Ga-Exendin-4 PET/CT and 68Ga-DOTATATE PET/CT which helped to make a conclusive diagnosis that the lesion in the gastric antrum was an ectopic insulinoma.

INTERVENTIONS

The patient was cured with minimally invasive laparoscopic resection of the tumor.

OUTCOMES

The symptoms were relieved and the blood glucose level remained normal after surgery.

CONCLUSIONS

This case shows that 68Gallium-exendin-4 PET/CT is useful for precise localization and thereby successful treatment of insulinoma, especially for occult insulinomas and those derived from an ectopic pancreas.

A Systematic Review of Proinsulin-Secreting Pancreatic Neuroendocrine Tumors

BACKGROUND

Pancreatic neuroendocrine tumors (PNETs) are a heterogeneous group of islet cell-derived neoplasms with a propensity toward hormone production. Among PNETs, proinsulin-secreting tumors (proinsulinomas) are exceedingly rare. The objective of this study is to collect and summarize the existing literature to provide a comprehensive evaluation of this uncommon disease.

METHODS

A systematic review was performed to characterize the clinicopathologic features of proinsulinoma. Using the electronic biomedical databases PubMed, Ovid Medline, and Embase, 316 publications were screened for relevance of which 14 were selected. We also present two patients with proinsulinoma treated at Yale New Haven Hospital.

RESULTS

Of the 16 patients included in the study, the mean age was 56.8 and there was a 2:1 female predominance. The majority of patients presented with symptomatic hypoglycemia with normal or low insulin levels. Median tumor diameter was 1.2 cm and 80% were located in the body and tail of the pancreas. Following resection, most patients had normalization of hormonal levels without recurrence (75%; 12/16).

CONCLUSION

Proinsulinomas are rare pancreatic neuroendocrine tumors that have the potential to cause hypoglycemia. While insulinomas and proinsulin-secreting tumors have many physiologic parallels, these cases illustrate several key distinctions in their diagnosis and management.

Is laparoscopic approach for pancreatic insulinomas safe? Results of a systematic review and meta-analysis

BACKGROUND

No consensus exists as to whether laparoscopic treatment for pancreatic insulinomas (PIs) is safe and feasible. The aim of this meta-analysis was to assess the feasibility, safety, and potential benefits of laparoscopic approach (LA) for PIs. The abovementioned approach is also compared with open surgery.

METHODS

A systematic literature search (MEDLINE, EMBASE, Cochrane Library, Science Citation Index, and Ovid journals) was performed to identify relevant articles. Articles that compare the use of LA and open approach to treat PI published on or before April 30, 2013, were included in the meta-analysis. The evaluated end points were operative outcomes, postoperative recovery, and postoperative complications.

RESULTS

Seven observational clinical studies that recruited a total of 452 patients were included. The rates of conversion from LA to open surgery ranged from 0%-41.3%. The meta-analysis revealed that LA for PIs is associated with reduced length of hospital stay (weighted mean difference, -5.64; 95% confidence interval [CI], -7.11 to -4.16; P < 0.00001). No significant difference was observed between LA and open surgery in terms of operation time (weighted mean difference, 2.57; 95% CI, -10.91 to 16.05; P = 0.71), postoperative mortality, overall morbidity (odds ratio [OR], 0.64; 95% CI, 0.35-1.17; P = 0.14], incidence of pancreatic fistula (OR, 0.86; 95% CI, 0.51-1.44; P = 0.56), and recurrence of hyperglycemia (OR, 1.81; 95% CI, 0.41-7.95; P = 0.43).

CONCLUSIONS

Laparoscopic treatment for PIs is a safe and feasible approach associated with reduction in length of hospital stay and comparable rates of postoperative complications in relation with open surgery.

Setting the bar for laparoscopic resection of sporadic insulinoma

BACKGROUND

Laparoscopic insulinoma resection (LIR) for sporadic disease is increasingly supported as a feasible and safe operation in small series of patients. To determine whether LIR is an acceptable alternative to the open operation, it is necessary to compare LIR to historical controls. The purpose of this study was to identify the skills and technology needed for LIR and establish outcome standards.

METHODS

A database of patients with benign sporadic insulinoma who underwent an open procedure at the Mayo Clinic was reviewed for demographics, imaging, operative/pathology reports, and outcomes. Outcomes were compared to a world-wide meta-analysis of patients who had undergone LIR reported in the English literature between 1996 and 2009.

RESULTS

Two hundred fifteen patients underwent a primary open operation for benign sporadic insulinoma. Solitary tumors were found in 97%. Meta-analysis identified 232 patients who underwent LIR. The open and LIR groups underwent comparable operations that included enucleations (64 vs. 68%) and distal pancreatectomies (28 vs. 35%) (p = 0.06). The mean estimated blood loss, operating time, and length of stay were comparable between the open and LIR groups (p = NS). Pancreatic fistula occurred more often in the LIR group (24 vs. 11%, p < 0.05). A curative operation was performed in 98% of control patients and in 99% of the LIR group (p = NS).

CONCLUSIONS

Multiple insulinomas are rare and a focused resection guided by imaging may be performed. LIR is associated with an increased incidence of pancreatic fistula. Success of LIR will depend on accurate multimodality preoperative imaging, skilled use of lap-US to replace palpation for localization, and safe methods to dissect the tumor adjacent to the pancreatic duct.

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.

Growth factor control of pancreatic islet regeneration and function

Type 1 and type 2 diabetes mellitus together are predicted to affect over 300 million people worldwide by the year 2020. A relative or absolute paucity of functional β-cells is a central feature of both types of disease, and identifying the pathways that mediate the embryonic origin of new β-cells and mechanisms that underlie the proliferation of existing β-cells are major efforts in the fields of developmental and islet biology. A poor secretory response of existing β-cells to nutrients and hormones and the defects in hormone processing also contribute to the hyperglycemia observed in type 2 diabetes and has prompted studies aimed at enhancing β-cell function. The factors that contribute to a greater susceptibility in aging individuals to develop diabetes is currently unclear and may be linked to a poor turnover of β-cells and/or enhanced susceptibility of β-cells to apoptosis. This review is an update on the recent work in the areas of islet/β-cell regeneration and hormone processing that are relevant to the pathophysiology of the endocrine pancreas in type 1, type 2 and obesity-associated diabetes.

[Giant insulinoma]

Islet-cell tumors are the most common neuroendocrine tumors that arise from the endocrine pancreas. They are typically benign and sporadic. Diagnosis is generally established late because clinical signs lack specificity. The insulinoma is difficult to localize since it is very small in size, often not exceeding 2cm. We report an exceptional case of giant insulinoma initially revealed by a pseudo-polycythemia in an 80-year-old man. He had been treated for hypertension for a few months. Routine biological investigations showed elevated hematocrit and haemoglobin, suggesting Vaquez disease. History taking revealed recent episodes of nocturnal agitation. On admission, he had reddish skin with a suspected enlarged spleen, but total blood volume was normal. Imaging studies showed a voluminous tumor located between the pancreas and the spleen. The presence of an insulinoma was confirmed on the basis of an elevated level of proinsulin at the time of an asymptomatic episode of hypoglycemia. Spleno-pancreatectomy was performed. Histopathological examination revealed a malignant, well-differentiated neuroendocrine malignant tumor.

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.