Giant pancreatic insulinoma. The bigger the worse? Report of two cases and literature review

Case Report: Giant insulinoma, a very rare tumor causing hypoglycemia

Insulinomas, with an incidence of 4 cases per million individuals per year, remain amongst the most frequent functional neuroendocrine tumors. The usual diameter of insulinomas usually remains under 3 cm of major axis. However, 44 exceptional cases of "giant insulinomas", have been reported worldwide, generally exceeding 9 cm in major axis. In this article, we report the case of a 38-year-old woman whom suffered from chronic hypoglycemia despite treatment with diazoxide. Abdominal CT-scan revealed a 88 x 73 mm mass located at the tail of the pancreas. Following surgical excision, histopathological analysis confirmed G1 neuroendocrine tumor, with focal cytoplasmic expression of insulin in tumor cells. After a 16-month follow-up period, the patient didn't address any specific complaint, and no disease recurrence and/or metastasis were observed. A ⁶⁸Ga-DOTATATE-PET scan was performed 6 months after surgery, which came back normal. Genetic evaluation has not been performed in our patient. The physiopathology of giant insulinomas remain unexplained, however with possible relationship with type 1 multiple endocrine neoplasia, sporadic somatic YY1 mutations and possible transformation of bulky non-functional pancreatic neuroendocrine tumors to a functional phenotype, with slow insulin secretion. While giant insulinomas remain rare in the literature, multicentric genetic analysis of tumor samples might reveal unique features of this rare subtype of neuroendocrine pancreatic tumors. Insulinomas of large size tend to have greater malignancy and higher rates of invasiveness. Careful follow-up, especially for liver and lymph node metastases, must be performed using functional imaging techniques to avoid disease relapse.

Is the Size of Insulinoma Predictive for its Endocrine Behavior? An Endoscopic Ultrasound Study

OBJECTIVE

Insulinoma is a rare tumor of the pancreas that can lead to spontaneous hypoglycemia due to excessive insulin secretion. Seventy-two-hour fast is the gold standard for finding the correct diagnosis. Endoscopic ultrasound (EUS) is an established examination method to identify the suspicious lesion. Previous studies correlate the measured size of insulinoma and their endocrine behavior. This study was designed to find a relation between these variables.

METHODS

We took the data of patients who had a histologically confirmed insulinoma after receiving an endoscopic ultrasound in our department. Size and echogenicity were correlated with the endpoint of the 72-hour fast and hormone levels.

RESULTS

A total of 45 patients were identified. Most insulinomas were small with a volume of<2 cm³ (median 1.15 cm³). There was no correlation between the duration of fasting, hormone levels, and the size of the insulinoma. In addition, in a subgroup analysis, no connection could be established between the size of the insulinoma and the amount of insulin released after oral glucose exposure. We found that homogeneous tumors were significantly smaller and had a lower Ki-67 index. Furthermore, there was a tendency towards a shorter duration for the 72-hour fast for the small tumors.

DISCUSSION

This data suggests that the measured size of insulinoma by EUS is not related to the time until termination of the 72-hour fast and measured hormone levels. The echogenicity seems more important, showing that homogenous tumors are an indicator of a higher differentiation, which can result in a shorter duration of the fasting period. The differences in the secretion behavior of the insulinomas could complicate the correlation of size and the 72-hour fast period.

Hypoglycemia in a Patient With a Polyhormonal Pancreatic Neuroendocrine Tumor With Evidence of Endocrine Progenitors

A 55-year-old woman with a large polyhormonal neuroendocrine tumor with unusual pathology is described. The patient presented with intermittent neuroglycopenic symptoms between more protracted asymptomatic periods occurring over the preceding 4 years. During a diagnostic 72-hour inpatient fast, she exhibited hypoglycemia at 70 hours after initiation. On computed tomography scan, a 6-cm mass was identified at the pancreatic head. The patient underwent a pylorus-preserving pancreaticoduodenectomy, and pathology was positive for cells staining for pancreatic polypeptide, insulin, and occasional double hormone (insulin plus pancreatic polypeptide)-positive cells. In addition, the tumor exhibited broad staining for ALDH1A3, a new marker of endocrine progenitors. This case serves to highlight the clinical and pathologic variability of insulin-producing tumors and raises the potential for cells in these tumors to exhibit hormone interconversion and progenitor-like states.

Giant insulinoma: report of a case and review of published reports

Background

Larger insulinomas are reportedly more likely to be malignant; however, their biological behavior has not been clearly elucidated. We here report the characteristics and treatment of a giant insulinoma with local invasion and lymph node metastasis. We also review published reports concerning the clinical features of giant insulinomas and comparing their grading with that of pancreatic neuroendocrine tumors.

Case presentation

A 71-year-old man was referred to our hospital for investigation of persistent hypoglycemia. On the current presentation, laboratory tests showed serum glucose, immunoreactive insulin, and C peptide concentrations of 45 mg/dL, 17.2 μIU/mL and 4.1 ng/mL, respectively. Dynamic magnetic resonance imaging showed a hypervascular tumor measuring 13.5 cm in the head of the pancreas. Computed tomography scanning demonstrated local invasion and lymph node involvement. He thus had Whipple’s triad, which is associated with malignant insulinoma. No distant metastases having been identified, pancreaticoduodenectomy was performed. Intraoperatively, three separate tumors were identified in the pancreatic head. Pathological examination showed all three tumors were pancreatic neuroendocrine tumors; the tumor cells in the largest mass were strongly immunoreactive for insulin. The Ki-67 index was 2–5% in most parts of the largest tumor and over 20% in the poorly differentiated areas. This tumor was classified as neuroendocrine carcinoma in accordance with the 2010 World Health Organization classification of pancreatic endocrine neoplasms. He remains free of evidence of recurrence 2 years postsurgery.

A review of published reports indicated that giant insulinomas are more malignant than smaller ones, and metastatic disease is found on presentation in 56% of patients with giant insulinomas; however, we were unable to identify any correlation between grade of pancreatic neuroendocrine tumor and biological behavior of giant insulinomas.

Conclusions

Giant insulinomas more frequently exhibit malignant behavior, such as local invasion, lymph node involvement, and liver metastasis, than smaller ones. However, there was no relationship between grade and rate of metastases or survival in this small case series. Identification of useful biological markers is necessary.

Concomitant existence of pheochromocytoma in a patient with multiple endocrine neoplasia type 1

Background

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal-dominant inherited disorder that is classically characterized by the presence of neoplastic lesions of the parathyroid glands, the anterior pituitary gland, and the pancreas. However, MEN1 with concomitant pheochromocytoma is extremely rare.

Case report

We report a case of MEN1 concomitant with pheochromocytoma. A 44-year-old Japanese man, who had undergone total parathyroidectomy due to primary hyperparathyroidism at the age of 18, was referred to our hospital with a complaint of a large abdominal tumor. He was diagnosed as having a giant insulinoma (maximum diameter 18 cm) in the pancreatic tail, five other non-functional neuroendocrine tumors in the pancreatic body and tail, multiple liver metastases of pancreatic neuroendocrine tumors, a pituitary prolactinoma, non-functional adrenal cortical adenomas, a pheochromocytoma in addition to a subcutaneous neurofibroma, and a cutaneous fibroma. The genetic screening revealed a deletion mutation at codons 83–84 in exon 2 of the MEN1 gene. He underwent distal pancreatectomy, splenectomy, cholecystectomy, right adrenalectomy, abdominal subcutaneous tumor excision, and cutaneous tumor biopsy for the purpose of tumor volume reduction. Extended right posterior segmentectomy with partial hepatectomy of S2, S3, and S8 was performed to resect residual tumors 9 months after the initial surgery. Although a newly formed liver metastasis was found 19 months after the hepatectomy, he is still alive 4 years and 4 months after the initial surgery.

Conclusions

We reported an extremely rare case of giant insulinoma and simultaneous occurrence of pheochromocytoma and adrenal cortical adenoma in the ipsilateral adrenal gland in a patient clinically and genetically diagnosed as having MEN1.

Diagnosis and surgical management of insulinomas in 33 consecutive patients at a single institution

PURPOSE

The purpose of this study was to evaluate the diagnosis and surgical management of insulinomas in a single-center setting.

METHODS

Demographic details, clinical presentation, preoperative diagnosis, surgical strategy, and outcomes of 33 consecutive patients who underwent surgery for insulinoma were analyzed retrospectively.

RESULTS

The median time from the first onset of symptoms to diagnosis was 24 months (range 3 days to 50 years). All cases presented with Whipple's triad and had a fasting insulin to glucose ratio higher than 0.33. The preoperative detection rates of transabdominal ultrasonography, CT, MRI, and EUS were 22 % (2/9), 72 % (23/32), 75 % (9/12), and 80 % (4/5), respectively. Intraoperative manual palpation localized all cases. Enucleation was performed in 58 % of cases (19/33), partial pancreatic resection in 39 % (13/33), and enucleation plus partial resection in 3 % (1/33). Pancreatic fistula was the most common complication and occurred in 15 patients (45 %), including seven grade A, five grade B, and three grade C fistulas. There was no mortality. When compared with partial pancreatectomy, enucleation held a significant advantage in operative time and operative bleeding, with no significant differences in demographic data and postoperative complications. During a median follow-up period of 32 months, two patients were lost to follow-up and the remaining 31 patients were without evidence of recurrence.

CONCLUSIONS

A fasting insulin release index larger than 0.3 is a reliable indicator for the diagnosis of insulinoma. Intraoperative palpation by an experienced surgeon can effectively complement an uncertain preoperative localization. Compared with partial pancreatic resection, enucleation showed significant benefit in terms of intraoperative blood loss and operation time.

Different Hormonal Expression Patterns Between Primary Pancreatic Neuroendocrine Tumors and Metastatic Sites

OBJECTIVES

Pancreatic neuroendocrine tumors (PNETs) are known to have heterogeneity in terms of their ability to produce multiple hormones. The aim of this study was to evaluate the heterogeneity of PNETs from the viewpoint of hormonal expression.

METHODS

The expressions of 4 representative hormones, gastrin, insulin, glucagon, and somatostatin, in both primary and metastatic lesions, were analyzed by immunohistochemical staining in 20 patients with metastatic PNETs (6 gastrinomas, 1 insulinoma, 1 glucagonoma, and 12 nonfunctioning PNETs [NF-PNETs]). Metastatic sites included lymph nodes in all 20 patients and liver metastasis in 7 patients (2 gastrinomas and 5 NF-PNETs).

RESULTS

There were 6 PNETs with multiple hormone secretion (30%), and positive expression of 1 or more hormones was found in 9 of 12 patients whose primary tumors were diagnosed as NF-PNETs. The positive concordance rate of the hormonal expression pattern between primary tumors and metastatic lymph nodes and between primary tumors and hepatic metastasis were 50% and 11%, respectively. Three patients had metastatic lesions with positive hormonal expression, whereas their primary tumors were negative.

CONCLUSIONS

Hormonal expressions are often different between the primary tumors and metastatic sites of PNETs.

Giant Malignant Insulinoma

The role of debulking resections in giant malignant insulinoma is still controversial. Here, we report the case of a 49-year-old patient woman with a giant malignant symptomatic insulinoma, who underwent debulking surgery, realizing a total pancreatectomy, splenectomy, partial gastrectomy and cholecystectomy.

Giant insulinoma in a 15-year-old man: A case report

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Giant insulinomas are extremely rare, especially among young patients.

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Tumor resection is the treatment of choice for giant insulinomas with benign features.

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Long-term follow-up is essential in benign giant insulinoma to detect the recurrence in the future

Introduction

Giant insulinomas are extremely rare pancreatic neuroendocrine tumor.

Presentation of case

A 15-year-old man presenting with acute onset of lightheadedness was found to have serum glucose of 1.5 mmol/L. The blood collected from the hypoglycemic episode showed an inappropriately high insulin and C-peptide level. Abdominal computerized tomography showed a 12.5 cm well-defined, lobulated hypervascular mass at pancreatic tail, without any evidence of metastasis. En bloc resection with distal pancreatectomy, and splenectomy was successfully performed. The pathological examination confirmed insulinoma, with benign characteristics. Follow-up after the procedure revealed neither hypoglycemic, nor hyperglycemia.

Conclusion

We report the youngest case of a giant insulinoma. Despite the size of the tumor, the pathological report confirmed the benign characteristics. However, long-term follow-up is still essential to detect recurrence in the future.

Clinical presentation in insulinoma predicts histopathological tumour characteristics

BACKGROUND

Insulinomas are rare neuroendocrine tumours (NETs) of the pancreas, characterized clinically by neuroglycopenic symptoms during periods of substrate deficiency. The gold standard test for diagnosing an insulinoma is a 72-h fast. However, the prognostic value of parameters in the standardized 72-h fast on histopathological tumour criteria and clinical presentation has not been examined.

METHODS

In thirty-three patients diagnosed with an insulinoma records, and data were investigated retrospectively. Histopathological tumour characteristics, including staging, grading and size, were reviewed. Grading was performed using Ki-67 index. Cut-off values for classical grading (G(clas)) were set at G1(clas) ≤ 2%, G2(clas) 3-20% & G3(clas) >20% and for modified grading (G(mod)) at G1(mod) <5%, G2(mod) 5-20% & G3(mod) >20%.

RESULTS

When G(mod) criteria were applied, the initial blood glucose was lower in GII/III(mod) patients compared to GI(mod) (2.8 ± 0.8 vs 3.8 ± 1.3 mmol/l; P = 0.046). Basal and end of fast levels of insulin (basal insulin 71 ± 61 vs 20 ± 16 mU/l; P < 0.001; end of fast insulin 77 ± 51 vs 21 ± 20 mU/l; P < 0.001) and c-peptide (basal c-peptide 5.4 ± 2.4 vs 2.7 ± 1.6 μg/l; P = 0.004; end of fast c-peptide 5.3 ± 2.4 vs 2.5 ± 1.4 μg/l; P = 0.001) were significantly higher in GII/III(mod) than in GI(mod). No differences between the groups were observed when G(clas) criteria were applied. Additionally, close correlations were observed between insulin concentration, Ki-67 index and tumour size.

CONCLUSION

This study shows an impact of histopathological tumour characteristics in patients suffering from an insulinoma on clinical presentation during a standardized 72-h fast. Lower initial blood glucose levels and higher concentrations of insulin and c-peptide are associated with worse tumour grading and larger tumour size.