Ectopic duodenal insulinoma: a very rare and challenging tumor type. Description of a case and review of the literature

Approach to the Patient: Insulinoma

Insulinomas are hormone-producing pancreatic neuroendocrine neoplasms with an estimated incidence of 1 to 4 cases per million per year. Extrapancreatic insulinomas are extremely rare. Most insulinomas present with the Whipple triad: (1) symptoms, signs, or both consistent with hypoglycemia; (2) a low plasma glucose measured at the time of the symptoms and signs; and (3) relief of symptoms and signs when the glucose is raised to normal. Nonmetastatic insulinomas are nowadays referred to as "indolent" and metastatic insulinomas as "aggressive." The 5-year survival of patients with an indolent insulinoma has been reported to be 94% to 100%; for patients with an aggressive insulinoma, this amounts to 24% to 67%. Five percent to 10% of insulinomas are associated with the multiple endocrine neoplasia type 1 syndrome. Localization of the insulinoma and exclusion or confirmation of metastatic disease by computed tomography is followed by endoscopic ultrasound or magnetic resonance imaging for indolent, localized insulinomas. Glucagon-like peptide 1 receptor positron emission tomography/computed tomography or positron emission tomography/magnetic resonance imaging is a highly sensitive localization technique for seemingly occult, indolent, localized insulinomas. Supportive measures and somatostatin receptor ligands can be used for to control hypoglycemia. For single solitary insulinomas, curative surgical excision remains the treatment of choice. In aggressive malignant cases, debulking procedures, somatostatin receptor ligands, peptide receptor radionuclide therapy, everolimus, sunitinib, and cytotoxic chemotherapy can be valuable options.

Ectopic insulinoma: a systematic review

Knowledge of ectopic insulinomas comes from single cases. We performed a systematic review through PubMed, Web of Science, Embase, eLibrary and ScienceDirect of all cases reported in the last four decades. We also describe one unreported patient. From 28 patients with ectopic insulinoma, 78.6% were female and mean age was 55.7 ± 19.2 years. Hypoglycaemia was the first symptom in 85.7% while 14.3% complained of abdominal pain or genital symptoms. Median tumour diameter was 27.5 [15-52.5] mm and it was localised by CT (73.1%), MRI (88.9%), [68Ga]Ga-DOTA-exedin-4 PET/CT (100%), 68Ga-labelled-DOTA-conjugated somatostatin analogue PET/TC (100%), somatostatin receptor scintigraphy (40%) and endoscopic ultrasound (50%). Ectopic insulinomas were located at duodenum (n = 3), jejunum (n = 2), and one respectively at stomach, liver, appendix, rectum, mesentery, ligament of Treitz, gastrosplenic ligament, hepatoduodenal ligament and splenic hilum. Seven insulinomas were affecting the female reproductive organs: ovary (n = 5), cervix (n = 2) and remaining tumours were at retroperitoneum (n = 3), kidney (n = 2), spleen (n = 1) and pelvis (n = 1). 89.3% underwent surgery (66.7% surgery vs. 33.3% laparoscopy) and 16% underwent an ineffective pancreatectomy. 85.7% had localized disease at diagnosis and 14.3% developed distant metastasis. Median follow-up time was 14.5 [4.5-35.5] months and mortality was reported in 28.6% with median time until death of 60 [5-144] months. In conclusion, ectopic insulinomas are presented as hypoglycaemia with female preponderance. Functional imaging [68Ga]Ga-DOTA-exedin-4 PET/CT and 68Ga-labelled-DOTA-conjugated somatostatin analogue PET/TC have very high sensitivity. Clinicians should be alert to the possibility of extra-pancreatic insulinomas when classic diagnostic tests and intraoperative pancreas exploration failed to locate the tumour.

Case presentation of 8-year follow up of recurrent malignant duodenal Insulinoma and lymph node metastases and literature review of malignant Insulinoma management

BACKGROUND

Insulinoma is an uncommon insulin-secreting neuroendocrine tumor that presents with severe recurrent hypoglycemia. Although cases of extrapancreatic insulinomas have been reported, the majority of insulinomas occur in the pancreas. The number of reported cases of ectopic insulinomas with follow-up assessments is limited and they do not report disease recurrence. The current report presents the first documented case of recurrent extrapancreatic insulinoma with 8 years of follow-up, provides relevant literature review, and proposes surveillance and treatment strategies.

CASE PRESENTATION

We describe an insulinoma localized in the duodenal wall of a 36-year-old female who presented in 2013 with weight gain and Whipple's triad and was successfully managed with duodenotomy and enucleation. She presented again in 2017 with recurrent Whipple's triad and was found to have metastatic disease localized exclusively to peripancreatic lymph nodes. Primary pancreatic insulinoma was not evident and her hypoglycemia resolved following lymph node dissection. Eight years after initial presentation continuous glucose monitoring (CGM) showed a trend for euglycemia, and PET-CT Gallium 68 DOTATATE scan evaluation indicated absence of recurrent disease.

CONCLUSION

Insulinomas are rare clinical entities and extrapancreatic insulinomas are particularly uncommon. Follow-up evaluation and treatment strategies for ectopic insulinoma recurrence presents a significant clinical challenge as the condition has hitherto remained undescribed in the literature. Available evidence in the literature indicates that lymph node metastases of intrapancreatic insulinomas likely do not change prognosis. Given the absence of long-term data informing the management and monitoring of patients with extrapancreatic insulinoma, we suggest patient education for hypoglycemic symptoms, monitoring for hypoglycemia with CGM, annual imaging, and a discussion with patients regarding treatment with octreotide or alternative somatostatin receptor analog therapies.

Successful surgical treatment of a patient with primary insulinoma of the liver

Insulinoma is the most frequent functional neuroendocrine tumor of the pancreas, which causes organic hyperinsulinism with severe hypoglycemia. There are no cases of primary insulinoma of the liver described. A 63-year-old female was admitted to our center presenting symptoms of severe hypoglycemia due to confirmed endogenic hyperinsulinism. None of the performed diagnostic procedures could reveal a pancreatic tumor. However, a pathologic mass in the sixth segment of the liver was detected. We performed arterial calcium stimulation that showed increased levels of insulin and c-peptide in almost all stimulated arteries. The highest and most prolonged peaks were detected at the points of the common hepatic artery and the right hepatic artery. After the surgical removal of the liver tumor, the blood glucose level was stabilized within the normal range. Post-operative pathomorphological investigation confirmed the diagnosis of a neuroendocrine tumor. The long-term survival results show correct treatment tactics without any signs of disease recurrence.

Pitfalls in the Detection of Insulinomas With Glucagon-Like Peptide-1 Receptor Imaging

PURPOSE

Physiological pancreaticoduodenal uptake of radiolabeled exendin-4 in Brunner glands of the proximal duodenum is the most common pitfall for false interpretation of glucagon-like peptide-1 receptor (GLP-1R) imaging. The aim of this study was to analyze the pancreaticoduodenal uptake in GLP-1R PET/CT and SPECT/CT images and to identify additional potential reading pitfalls in patients with suspected insulinoma.

METHODS

A post hoc analysis of a prospective study, including 52 consecutive patients, was performed. All patients underwent 1 Ga-exendin-4 PET/CT and 2 In-exendin-4 SPECT/CT scans (4 and 72 hours postinjection) in a randomized crossover order. Three board-certified nuclear medicine physicians read all scans independently. They were unaware of other results. Reference standard was surgery with histopathological confirmation of an insulinoma/nesidioblastosis and normalization of blood glucose levels after surgery.

RESULTS

There were no false-positive readings. However, there were a number of false-negative PET/CT and SPECT/CT readings, respectively: (1) due to false interpretation of uptake in the pancreaticoduodenal region (falsely interpreted as physiological uptake in Brunner glands instead of an insulinoma in 0.6% vs 9.0%), (2) due to ectopic insulinoma (0% vs 2.6%), (3) due to small insulinoma (1.9% vs 5.1%), (4) due to insulinoma overlap with kidneys (1.9% vs 4.5%), and (5) due to nesidioblastosis (0.6% and 1.9%). Pitfalls were identified in all GLP-1R PET/CT and SPECT/CT scans.

CONCLUSIONS

Peripancreatic uptake, small size of an insulinoma, insulinoma overlap with kidneys, and presence of nesidioblastosis are potential pitfalls in GLP-1R imaging, which can lead to false reading results.

Ectopic insulinoma: case report

BACKGROUND

Ectopic insulinoma is a rare entity that is difficult to diagnose before surgery. This article reports two cases of ectopic insulinoma.

CASE PRESENTATION

Two patients manifested recurrent hypoglycemia with a typical Whipple triad. In terms of the qualitative diagnosis, the oral glucose tolerance test (OGTT) suggested a diagnosis of hyperinsulinemic hypoglycemia. However, preoperative imaging did not show a significant mass in the pancreas. In one patient, preoperative abdominal enhanced volume perfusion computed tomography (CT), somatostatin receptor imaging and ^99mTc-HYNIC-TOC SPECT/CT revealed a mass with a rich blood supply anterior to the duodenum. In the other patient, preoperative enhanced CT, magnetic resonance imaging (MRI) and ⁶⁸Ga-Exendin-4 PET/CT showed a mass above the spleen. After surgical removal of the tumor, both patients received a confirmed diagnosis of neuroendocrine tumors by postoperative pathology. The symptoms of hypoglycemia were relieved after surgery, and the blood glucose level was significantly increased.

CONCLUSION

Ectopic insulinoma is difficult to locate before surgery. ⁶⁸Ga-Exendin-4 PET/CT has a high diagnostic value. Surgical removal of the lesion is main treatment.

Immunohistochemical Biomarkers of Gastrointestinal, Pancreatic, Pulmonary, and Thymic Neuroendocrine Neoplasms

Neuroendocrine neoplasms (NENs) are a heterogeneous group of epithelial neoplastic proliferations that irrespective of their primary site share features of neural and endocrine differentiation including the presence of secretory granules, synaptic-like vesicles, and the ability to produce amine and/or peptide hormones. NENs encompass a wide spectrum of neoplasms ranging from well-differentiated indolent tumors to highly aggressive poorly differentiated neuroendocrine carcinomas. Most cases arise in the digestive system and in thoracic organs, i.e., the lung and thymus. A correct diagnostic approach is crucial for the management of patients with both digestive and thoracic NENs, because their high clinical and biological heterogeneity is related to their prognosis and response to therapy. In this context, immunohistochemistry represents an indispensable diagnostic tool that pathologists need to use for the correct diagnosis and classification of such neoplasms. In addition, immunohistochemistry is also useful in identifying prognostic and theranostic markers. In the present article, the authors will review the role of immunohistochemistry in the routine workup of digestive and thoracic NENs.

Four Neuroendocrine Tumor Types and Neuroendocrine Carcinoma of the Duodenum: Analysis of 203 Cases

BACKGROUND

Several types of neuroendocrine neoplasms (NENs) have been described in the duodenal tract, from low-grade tumors (NETs) to high-grade neuroendocrine carcinomas (NECs). A comprehensive analysis of histology, hormonal profile and prognostic parameters of a sufficiently large duodenal NEN series to cover all main kinds of neoplasms is however lacking.

METHODS

We collected a retrospective series of 203 duodenal wall and ampullary region NENs, from six specialized endocrine pathology centers. All were characterized histopathologically and histochemically, and 190 were followed for a median of 9 years.

RESULTS

Twenty-seven poorly differentiated NECs, mostly from the ampullary region, were identified and shown to lead to patient demise in a median of 10 months. Among 176 NETs, four subtypes were characterized, including 20 gastrinomas, 37 ampullary-type somatostatin-producing NETs (ASTs), 12 gangliocytic paragangliomas (GPs) and 106 nonfunctioning NETs (nfNETs). ASTs and GPs were mostly localized in the ampullary/periampullary region, while gastrinomas and nfNETs were mainly from the proximal duodenum. ASTs and gastrinomas showed high rates of local infiltration (especially lymphoinvasion and deep duodenal wall/pancreatic tissue invasion) and lymph node metastasis, while nfNETs had significantly lower and more size-dependent local invasive potential. Disease-specific survival differed significantly between NETs and NECs, though not among NET subtypes. NET cases with distant metastases (n = 23) were significantly associated with larger size, higher proliferative grade, lymphovascular invasion, deep invasion and local lymph node metastasis.

CONCLUSION

Our careful analysis of a large series of duodenal NENs identified five histologically and prognostically different histotypes of potential clinical relevance.

Upregulation of INS-IGF2 read-through expression and identification of a novel INS-IGF2 splice variant in insulinomas

Fusion transcripts arising from the combination of exons residing on neighboring genes on the same chromosome may give rise to chimeric or novel proteins. Such read-through transcripts have been detected in different cancers where they may be of pathogenetic interest. In this study, we describe for the first time the expression of a read-through transcript in insulinomas, a functioning neuroendocrine pancreatic neoplasm. The read-through transcript INS-IGF2, composed of exons from the two genes proinsulin precursor (INS) and insulin‑like growth factor 2 (IGF2), both mapping to chromosomal subband 11p15.5, was highly expressed in the two insulinomas analyzed. More precisely, version 2 of the INS-IGF2 transcript was expressed, indicating possible expression of the chimeric INS-IGF2 protein. We further identified a novel splice variant of the INS-IGF2 read-through transcript in one of the insulinomas, composed of exon 1 of INS3 and exons of IGF2. In the same tumor, we found high expression of INS3 and the presence of the A allele at SNP rs689. SNP rs689 has been previously described to regulate splicing of the INS transcript, indicating that this regulatory mechanism also affects splicing of INS-IGF2. The identification of the INS-IGF2 read-through transcript specifically in tumor tissue but not in normal pancreatic tissue suggests that high expression of INS-IGF2 could be neoplasia‑specific. These results may have potential clinical applications given that the read-through transcript could be used as a biomarker in insulinoma patients.

Laparoscope resection of retroperitoneal ectopic insulinoma: A rare case

Ectopic insulinoma is a very rare and dormant tumor. Here we report the case of a 79-year-old female who presented with repeated episodes of hypoglycemia and was diagnosed with insulinoma based on laboratory and imaging examinations. Computed tomography and positron emission tomography revealed a tumor in the retroperitoneum under and left of the hepatoduodenal ligament, which was resected successfully using a laparoscopic approach. Pathologic results revealed an ectopic insulinoma, which was confirmed immunohistochemically. Ectopic insulinomas are accompanied by hypoglycemia that can be misdiagnosed as drug- or disease-induced. These tumors are difficult to diagnose and locate, particularly in atypical cases or for very small tumors. Synthetic or targeted examinations, including low blood glucose, elevated insulin, proinsulin, and C-peptide levels, 48-h fasting tests, and relevant imaging methods should be considered for suspected cases of insulinoma. Surgery is the treatment of choice for patients with insulinoma, and laparoscopic resection is a feasible and effective method for select ectopic insulinoma cases.

The imaging of insulinomas using a radionuclide-labelled molecule of the GLP-1 analogue liraglutide: a new application of liraglutide

Objective

This study explores a new, non-invasive imaging method for the specific diagnosis of insulinoma by providing an initial investigation of the use of ¹²⁵I-labelled molecules of the glucagon-like peptide-1 (GLP-1) analogue liraglutide for in vivo and in vitro small-animal SPECT/CT (single-photon emission computed tomography/computed tomography) imaging of insulinomas.

Methods

Liraglutide was labelled with ¹²⁵I by the Iodogen method. The labelled ¹²⁵I-liraglutide compound and insulinoma cells from the INS-1 cell line were then used for in vitro saturation and competitive binding experiments. In addition, in a nude mouse model, the use of ¹²⁵I-liraglutide for the in vivo small-animal SPECT/CT imaging of insulinomas and the resulting distribution of radioactivity across various organs were examined.

Results

The labelling of liraglutide with ¹²⁵I was successful, yielding a labelling rate of approximately 95% and a radiochemical purity of greater than 95%. For the binding between ¹²⁵I-liraglutide and the GLP-1 receptor on the surface of INS-1 cells, the equilibrium dissociation constant (K_d) was 128.8±30.4 nmol/L(N = 3), and the half-inhibition concentration (IC₅₀) was 542.4±187.5 nmol/L(N = 3). Small-animal SPECT/CT imaging with ¹²⁵I-liraglutide indicated that the tumour imaging was clearest at 90 min after the ¹²⁵I-liraglutide treatment. An examination of the in vivo distribution of radioactivity revealed that at 90 min after the ¹²⁵I-liraglutide treatment, the target/non-target (T/NT) ratio for tumour and muscle tissue was 4.83±1.30(N = 3). Our study suggested that ¹²⁵I-liraglutide was predominantly metabolised and cleared by the liver and kidneys.

Conclusion

The radionuclide ¹²⁵I-liraglutide can be utilised for the specific imaging of insulinomas, representing a new non-invasive approach for the in vivo diagnosis of insulinomas.