Insulinoma. An immunocytochemical and morphologic analysis of 95 cases

A Clinical Case of Insulinoma Presenting with Postprandial Hypoglycemia in a Patient with a History of Gastric Bypass Surgery

A 61-year-old man with a history of total gastrectomy for cancer with Roux-en-Y reconstruction showed severe postprandial hypoglycemia accompanied by endogenous hyperinsulinemia. Abdominal ultrasonography and contrast-enhanced computed tomography showed no abnormal findings in the pancreas. A selective arterial secretagogue injection test showed the marked induction of serum immunoreactive insulin when calcium was injected into the splenic artery. A pathological analysis following distal pancreatectomy with splenectomy revealed a pancreatic neuroendocrine microadenoma containing insulin-producing cells in the resected pancreas. This case highlights the importance of carefully evaluating refractory and severe hypoglycemia in patients with a history of gastric surgery to exclude insulinoma.

Surgical Management, Preoperative Tumor Localization, and Histopathology of 80 Patients Operated on for Insulinoma

INTRODUCTION

Diagnosis and pathological classification of insulinomas are challenging.

AIM

To characterize localization of tumors, surgery outcomes, and histopathology in patients with insulinoma.

METHODS

Patients with surgically resected sporadic insulinoma were included.

RESULTS

Eighty patients were included. Seven had a malignant tumor. A total of 312 diagnostic examinations were performed: endoscopic ultrasonography (EUS; n = 59; sensitivity, 70%), MRI (n = 33; sensitivity, 58%), CT (n = 55; sensitivity, 47%), transabdominal ultrasonography (US; n = 45; sensitivity, 40%), somatostatin receptor imaging (n = 17; sensitivity, 29%), 18F-fluorodeoxyglucose positron emission tomography/CT (n = 1; negative), percutaneous transhepatic venous sampling (n = 10; sensitivity, 90%), arterial stimulation venous sampling (n = 20; sensitivity, 65%), and intraoperative US (n = 72; sensitivity, 89%). Fourteen tumors could not be visualized. Invasive methods were used in 7 of these 14 patients and localized the tumor in all cases. Median tumor size was 15 mm (range, 7 to 80 mm). Tumors with malignant vs benign behavior showed less staining for insulin (3 of 7 vs 66 of 73; P = 0.015) and for proinsulin (3 of 6 vs 58 of 59; P < 0.001). Staining for glucagon was seen in 2 of 6 malignant tumors and in no benign tumors (P < 0.001). Forty-three insulinomas stained negative for somatostatin receptor subtype 2a.

CONCLUSION

Localization of insulinomas requires many different diagnostic procedures. Most tumors can be localized by conventional imaging, including EUS. For nonvisible tumors, invasive methods may be a useful diagnostic tool. Malignant tumors showed reduced staining for insulin and proinsulin and increased staining for glucagon.

Concurrent Adult-Onset Diffuse β-Cell Nesidioblastosis and Pancreatic Neuroendocrine Tumor: A Case Report and Review of the Literature

Nesidioblastosis is an uncommon cause of organic persistent hyperinsulinemic hypoglycemia in adults. We report a case of adult-onset diffuse β-cell nesidioblastosis in a 49-year-old woman who was status-post Roux-en-Y gastric bypass and distal pancreatectomy for a well-differentiated pancreatic neuroendocrine tumor. While the neuroendocrine tumor was suspected to be an insulinoma, persistent hypoglycemia postoperatively suggested either incomplete resection or a second pancreatic neoplasm. Completion pancreatectomy revealed islet β-cell hyperplasia and nuclear pleomorphism consistent with β-cell nesidioblastosis. The patient's blood glucose levels normalized after completion pancreatectomy. While β-cell nesidioblastosis and insulinomas can coexist in the same patient, pathologists should be aware of β-cell nesidioblastosis as a potential cause for hyperinsulinemic hypoglycemia and should exclude it in patients who have not shown definitive clinical response after surgical excision of a pancreatic neuroendocrine tumor.

Diagnosis of Zollinger-Ellison syndrome in the era of PPIs, faulty gastrin assays, sensitive imaging and limited access to acid secretory testing

In recent years the diagnosis of Zollinger-Ellison syndrome (ZES) has become increasingly controversial with several new approaches and criteria proposed, differing from the classical biochemical criterion of inappropriate hypergastrinemia (i.e., hypergastrinemia in the presence of hyperchlorhydria) (Table 1). These changes have come about because of the difficulty and potential dangers of stopping proton pump inhibitors (PPIs) for gastric acid analysis; the recognition than many of the current assays used to assess gastrin concentrations are unreliable; the development of sensitive imaging modalities that detect neuroendocrine tumors (NETs) including an increasing number of the primary gastrinomas; the increased use of percutaneous or endoscopic ultrasound (EUS)-directed biopsies/cytology and the general lack of availability of acid secretory testing. In this article we will discuss the basis for these controversies, review the proposed changes in diagnostic approaches and make recommendations for supporting the diagnosis of ZES in the modern era.

Giant insulinoma: a report of 3 cases and review of the literature

Insulinoma is a rare pancreatic neuroendocrine tumor that is usually described as benign, sporadic, and very small (<2 cm). However, there have been rare case reports of insulinoma presenting as a giant tumor. We describe 3 cases of giant insulinomas, all of which developed liver metastases. The patients were aged 38, 63, and 67 years. Clinically, all patients presented with Whipple's triad associated with a large mass located in the pancreatic tail. The tumors ranged in size from 10 to 15 cm. On microscopic examination, the tumors were well differentiated with amyloid deposition ranging between 20% and 30%. Immunohistochemically, all 3 tumors showed strong diffuse expression of chromogranin and synaptophysin, whereas they were only focally positive for insulin. One patient developed liver recurrence 3 years after resection of the primary tumor yet remained asymptomatic without treatment. Another patient with liver recurrence underwent right hepatectomy and has been free of disease for 2 years. The third patient died of metastatic disease 13 years after initial surgery. Giant insulinomas are characterized by focal expression of insulin and high rates of liver metastases. Long-term follow-up is mandatory in these patients, as recurrence is expected after primary surgery.

Diagnosis of Zollinger-Ellison syndrome: Increasingly difficult

In the present paper the increasing difficulty of diagnosis of Zollinger-Ellison syndrome (ZES) due to issues raised in two recent papers is discussed. These issues involve the difficulty and need to withdraw patients suspected of ZES from treatment with Proton Pump Inhibitors (omeprazole, esomeprazole, lansoprazole, rabeprazole, pantoprazole) and the unreliability of many gastrin radioimmunoassays. The clinical context of each of these important issues is reviewed and the conclusions in these articles commented from the perspective of clinical management.

[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.

Ultrasonography of the pancreas. 1. Conventional imaging

Ultrasound imaging has made significant advances in recent years and plays an important role in the detection, characterization and staging of pancreatic diseases. Conventional ultrasonography (US) is a noninvasive imaging modality, which continues to be the first diagnostic step in the evaluation of the pancreas. Over its various decades of application, US have detected pancreatic pathology of great diversity. This article reviews the wide utility of US and the many examinations techniques, such as filling the stomach with water, changing the patient's position or suspending inspiration or expiration, allowing us to visualize all portions of the pancreas in a high percentage of patients.

Nonductal neoplasms of the pancreas

Although the majority of pancreatic neoplasms are infiltrating ductal adenocarcinomas or other neoplasms with ductal differentiation, neoplasms with acinar, endocrine, mixed, or uncertain differentiation constitute a diverse and distinctive group. The most common and best-characterized nonductal neoplasms are pancreatic endocrine neoplasm, acinar cell carcinoma, pancreatoblastoma, and solid pseudopapillary neoplasm. This review details the clinical and pathologic features of these nonductal neoplasms, highlighting diagnostic criteria including the use of specific immunohistochemical stains to define the cellular differentiation of the neoplasms.

[Pancreatic insulinomas]

Insulinoma is the most frequent neuroendocrine pancreatic tumor. In the present study, the clinical and immunohistochemical results of 20 patients who underwent surgery between January 1986 and December 2004 were evaluated. Clinical presentation, laboratory data, imaging studies, aspects of the surgical technique, complication rates and medium- and long-term follow-up were analyzed. Surgical treatment was recommended in all patients based on presenting symptoms and laboratory signs of hypoglycemia and hyperinsulinemia. In 15 patients, the lesion was identified preoperatively. In the 5 remaining patients, intraoperative palpation and ultrasonography were used to locate the lesion. The most frequently performed surgical procedures were pancreatic resection in 10 patients and laparotomic enucleation in the remaining 10. Laparoscopy was used in two patients. Two patients developed diabetes mellitus. The most frequent surgical complication was pancreatic fistula. No mortality was observed in the present series. Symptom reversion, characterized by disappearance of Whipple's triad and normal or increased glycemia values compared with preoperative values, was observed in all patients.

Multihormonality and entrapment of islets in pancreatic endocrine tumors

We analyzed pancreatic endocrine tumors (PETs) from 200 patients for the incidence of multihormonality and entrapped islets and correlated the results with clinicopathological features. Our series included 86 cases (43%) of functioning PET and 114 cases (57%) of nonfunctioning PET. Classified according to the WHO classification, there were 32 well-differentiated benign PETs, 85 well-differentiated PETs with uncertain behavior, and 83 well-differentiated malignant PETs. All tumors were immunostained for pancreatic hormones (insulin, glucagon, somatostatin, and pancreatic polypeptide) and for additional hormones such as gastrin, vasoactive intestinal polypeptide, calcitonin, seratonin, and adrenocorticotropic hormone. Multihormonality was found in 34% of all PETs and it was a frequent finding in the tumors of the uncertain behavior (38.8%) group. Islet entrapment was found in 57 tumors (28.5%) and was significantly more frequent in PETs with uncertain and malignant behavior than benign ones (p=0.01). In 57 cases, we also investigated whether ductule entrapment accompanied islet entrapment. Of these 57 tumors, 45 (79%) tumors had accompanying ductule entrapment. Ductule entrapment did not show significant correlation with malignancy and was a more frequent finding in nonfunctioning tumors. We conclude that the incidence of multihormonality in PETs is not as high as suggested previously and islet entrapping may reflect aggressive tumor growth and may be a complementary criterion for predicting the biological behavior of PETs.

[Pancreatic insulinomas: diagnosis and treatment]

BACKGROUND

Despite its rarity, the insulinoma is the most common pancreatic neuroendocrine tumor.

OBJECTIVE

Analyze clinical and immunohistochemical data from surgical resection of the pancreas insulinoma.

METHOD

Twelve cases are described, concerning surgical aspects, complications and medium-long term outcome of patients. They underwent surgical treatment due to clinical suspicion and biochemical diagnosis of hypoglycemia and hyperinsulinism.

RESULTS

The insulinoma was identified preoperatively in seven patients, while intraoperative ultrasonography and palpation were necessary for diagnosis in the other cases. Eight patients underwent pancreatic resection and pancreatic leak was observed in seven cases. Two patients developed diabetes mellitus and no mortality occurred in the current series.

CONCLUSION

All patients presented satisfactory outcome and remained asymptomatic with normal glicemia levels.

Protocol for the examination of specimens from patients with endocrine tumors of the pancreas, including those with mixed endocrine and acinar cell differentiation: a basis for checklists. Cancer Committee of the College of American Pathologists

No Abstract Available

Pancreatic endocrine tumour: a 22-year clinico-pathological experience with morphological, immunohistochemical observation and a review of the literature

The clinico-pathological features of 53 Chinese patients (27 males; 26 females) with pancreatic endocrine tumours were studied. The age range was from 14 to 78 years old (mean: 48 years) with the modal peak in the sixth decade for both sexes. Pancreatic endocrine tumours accounted for 14% of the primary pancreatic tumours operated on in Queen Mary Hospital. The autopsy incidence was 0.11%. Seventy-two per cent (38 cases) of the tumours were clinically functioning, comprising 33 insulinomas, three gastrinomas and two glucagonomas. A rare case of malignant gastrinoma associated with Cushing's syndrome was also documented. The functional tumours were seen in the younger patients. The calculated annual incidence of clinically significant tumours was approximately 0.2 per 100,000 population. There was no correlation between the site, functional status and histological patterns of the tumours. Seventy-two per cent of the tumours showed a trabecular pattern. Calcification was present in 5.7% (three cases); two such cases being gastrinomas. Amyloid was found in 25% of tumours, chiefly (92%) in the insulinomas. The main difficulty encountered in diagnosis was distinguishing between solid and cystic tumours of the pancreas. The incidence of malignancy was 15% and the histological features were poor predicative indicators of malignant potential. The metastatic pancreatic endocrine tumours were often detected in the liver and lymph nodes. Immunohistochemical stains showed evidence of multi-hormone production in 18% of cases and all tumours showed a positive reaction to at least one of the six markers, namely, neuron-specific enolase (NSE), chromogrannin (CG), synaptophysin (SYN), insulin (INS), glucagon (GLU) or somatostatin (SOM). The three panendocrine markers (NSE, SYN, CG) were satisfactory for initial screening of the endocrine nature of the tumours if used in combination, as 92% of tumours were positive for at least one of these three markers.

Comparative cytologic features of pancreatic acinar cell carcinoma and islet cell tumor

Acinar cell carcinoma (ACC) and islet cell tumor (ICT), both rare pancreatic neoplasms, can be diagnosed accurately and rapidly with the use of imaging-guided fine-needle aspiration biopsies. The specific cytologic features of these tumors are described in a series of 17 patients, and histologic and immunocytochemical correlations are discussed. Important cytologic findings in ACC are loosely cohesive clusters with cells having uniform nuclei and prominent nucleoli, cytoplasm is finely granular and eosinophilic. Islet cell tumors show many single cells, occasional rosettes, uniform nuclei, sometimes binucleate, dense basophilic cytoplasm. Chromogranin is often positive (80%) in ICT. Trypsin and chymotrypsin were often positive (71%) in ACC. Histology was confirmatory in all cytology cases. The recognition of cytologic features in conjunction with immunocytochemical studies can increase the diagnostic sensitivity for these two rare tumors.

Duct-acinar-islet cell tumor of the pancreas

A case of a rare pancreatic tumor, duct-acinar-islet cell tumor is presented. The tumor was incidentally found in the pancreatic body on computed tomography of a 21 year old male suffering from mumps. It was well demarcated from surrounding pancreas, and spherical in shape, measured 2.5 cm in diameter. Histologic and immunohistochemical examinations showed the tumor to consist of three distinct cell populations: duct, acinar and islet cells. Small cell nests consisting of these cellular components, either solely of one cell type or mixed of the three cell types, were separated by broad desmoplastic stroma. Islet (endocrine) cells, which were most predominant, were arranged in a trabecular pattern or small cell nests. Most of them were positive for glucagon, and a few cells expressed insulin, somatostatin, serotonin or pancreatic polypeptide. These cells were distributed randomly within the cell nests. Ducts, some of which contained goblet cells, were found among the endocrine cell nests. Duct-islet complexes were also observed. The acinar cells were the least conspicuous component. They expressed pancreatic alpha-amylase. An electron microscopic examination revealed duct cells with intercellular attachments and interdigitations, endocrine cells containing secretory granules, and acinar cells with zymogen granules. No definite evidence suggesting malignancy could be obtained.

Calcitonin-producing insulinoma: clinical, immunocytochemical and cytogenetical study

The case of a patient with a large goitre associated with hypercalcitoninaemia and fasting hypoglycaemia is reported. Pentagastrin (PG) test was negative. Repeated measurements of fasting glycaemia, insulin and C peptide established the diagnosis of insulinoma. After localization by endoscopic ultrasonography, a distal pancreatectomy was performed and a small insulinoma was recovered. Glycaemia and calcitonin (CT) became normal. The tumour cells displayed a strong immunoreactivity for insulin and CT. Cytogenetical evaluation of the tumour revealed a translocation t(1;9) (p13;p22).

Ultrastructural study of a black insulinoma

A case of black insulinoma is reported. The color was due to a cytoplasmic pigment. Immunostaining for neuron-specific enolase and chromogranin was positive in the tumor cells, and the pigment granules themselves reacted with the chromogranin antibody. Numerous beta cell type dense core granules as well as atypical granules were found by electron microscopy. An important finding was that the dense core granules contribute to the lipofuscin pigment formation.

Comparison between liver and serum concentrations of mannan binding protein

AIMS

To investigate staining patterns for mannan binding protein (MBP) by immunocytochemistry in liver biopsy specimens from patients with various hepatic disorders; to measure the serum MBP concentration in the patients at the time of biopsy; and to compare these to define further the role of MBP in disease.

METHODS

Fifty seven consecutive patients with a variety of types of liver disease were studied. Fresh liver biopsy specimens were immunostained with anti-MBP and graded for intensity of staining. Serum MBP concentrations were measured on samples obtained on the day of biopsy, as were a full range of liver blood tests.

RESULTS

MBP was only detectable in liver biopsy specimens from patients with morphological evidence of liver disease. MBP was most prominent in the livers of patients with severe alcoholic liver disease; livers harbouring metastases or showing biliary disease had moderate concentrations. Patients with liver disease were more likely to have raised serum MBP concentrations, but there was no correlation between these values and those found in the biopsy specimens. There was also no significant correlation between either of these concentrations and liver blood test abnormalities.

CONCLUSIONS

Patients with liver disease tend to have raised MBP concentrations in both the liver and serum, but the exact relation between the two is as yet undefined.

Nonfunctioning pancreatic endocrine tumors. An immunohistochemical and electron microscopic analysis of 26 cases

Twenty-six patients with non-functioning pancreatic endocrine tumor (NFPET) were operated on during a 22-year period (1968-1990) at PUMC Hospital, Beijing. Of these, 19 were female and 7 were male with a mean age of 33 years. All these tumors, including 12 malignant and 14 benign, were solitary, and most of them were well-encapsulated. Immunohistochemical staining showed 23 (88.5%) containing 1-4 kinds of peptide hormone and 18 (69.2%) being multihormonal. In 7 of the 9 tumors subjected to electron microscopic study, various amounts of neurosecretory granules were found. Tumors of this series were clinically silent, but they contained some immunoreactive peptides, although the amount of the peptides varied from tumor to tumor.

Endocrine neoplasms of the pancreas: a clinicopathologic study of 24 cases and immunohistochemical remarks

A total of 24 patients with endocrine neoplasms of the pancreas were clinicopathologically and immunohistochemically studied. They consisted of 18 patients with adenoma and 6 with carcinoma. Of the 24 patients, 13 developed attacks of hypoglycemia due to hyperinsulinemia, and 1 developed an uncontrollable duodenal ulcer caused by the hypersecretion of gastrin, however, the remaining 10 were asymptomatic. No prediction could be made as to the site of origin of the tumors. A clear difference was seen between adenoma and carcinoma in the size of the mass, the mean greatest diameter of the 18 adenoma cases being 1.7 cm, while that of the 6 carcinoma cases was 7.3 cm. One of the 13 insulinomas and a gastrinoma was malignant, while all 24 tumors were positive for neuron-specific enolase. The 13 insulinomas were diffusely positive for insulin and 5 were also shown to be focally immunoreactive for gastrin, with 3 also being immunoreactive for somatostatin and 2 for pancreatic polypeptide. The gastrinoma showed immunoreactivity for somatostatin, insulin, pancreatic polypeptide, and glucagon in addition to a positivity to gastrin. The above findings thus indicate the multiple hormone synthesis of endocrine neoplasms of the pancreas.

Islet amyloid polypeptide in insulinoma and in the islets of the pancreas of non-diabetic and diabetic subjects

Amyloid deposition is a common pathological feature in insulinoma and in the islets of the pancreas in type-2 diabetic patients. The present immunohistochemical study revealed that normal B-cells, insulinoma, and amyloid deposits in insulinoma and diabetic pancreatic islets were commonly immunoreactive with antiserum to C-terminal synthetic tetradecapeptide of human islet amyloid polypeptide (IAPP) (24-37). Amyloid fibrils in insulinoma were also positive to IAPP by immunoelectron microscopy. A high level of IAPP was detected in the plasma and tissue of a insulinoma patient by radioimmunoassay suggesting that amyloid deposition in insulinoma is due to overproduction of IAPP. Amyloid deposits immunoreactive to IAPP were also seen in all diabetic pancreatic islets, but in no non-diabetic islets. There was much amyloid deposition in the islets of severe diabetics, whose B-cells demonstrated decreased immunoreactivities for IAPP and insulin. The IAPP content of the pancreas was 649.0 and 847.7 pg/mg wet weight in each of two diabetic patients, and 1034.6 and 1447.7 pg/mg wet weight in two non-diabetic patients. The present study revealed that IAPP is a bioactive peptide secreted from islet B-cells and are amyloidogenic peptide concerned in diabetogenensis and/or the progression of type-2 diabetes mellitus.

Islet cell tumor

A case of islet cell tumor occurring in a patient with the multiple endocrine neoplasia type I syndrome is reported. Immunostaining for insulin was strongly positive in the tumor cells. Numerous dense-core granules of endocrine caliber were identified ultrastructurally. Morphometric analysis of the secretory granules in 20 islet cell tumors gave a granule size of 182 +/- 52 nm (mean +/- standard deviation).

Functioning insulinoma--incidence, recurrence, and long-term survival of patients: a 60-year study

For the 60-year period from 1927 through 1986, we assessed the incidence, recurrence, and long-term survival among all Mayo Clinic patients with histologically confirmed functioning insulinoma. With use of the complete medical record system at Mayo and the comprehensive epidemiologic data base of residents of Olmsted County, Minnesota, we found 224 patients in whom an initial pancreatic exploration at Mayo had confirmed the presence of insulinoma. The median age (and range) of these patients at surgical diagnosis was 47 (8 to 82) years, and 59% were female patients. During the study period, eight cases of insulinoma occurred among residents of Olmsted County; their age and gender distributions were similar to those of the total cohort. The incidence of insulinoma among residents of Olmsted County increased during the study period to a stable level during the last 2 decades of 4 cases per 1 million person-years. For the total cohort, 7.6% had multiple endocrine neoplasia type I (MEN I), and 5.8% had malignant insulinoma. The risk of recurrence was greater among patients with MEN I (21% at 10 and 20 years) than in those without MEN I (5% at 10 years and 7% at 20 years). Although survival of the total cohort was not significantly impaired, it was significantly worse than expected for patients with malignant insulinoma (29% versus 88% expected at 10 years postoperatively). We conclude that insulinoma is less rare than previously suspected. After successful surgical removal, the long-term risk of recurrent insulinoma is relatively high in patients with MEN I; for patients with benign disease, the long-term survival is normal.

Upper abdominal neoplasms: an introduction and selected references

The organs in the upper half of the abdominal cavity can give rise to a highly heterogeneous collection of neoplasms that encompasses a broad spectrum of clinical features, light microscopic appearances, immunostaining properties, and fine structure. Because of the anatomic proximity of the viscera in this region, the differential diagnosis of an upper abdominal mass may include consideration of tumors that arise from the stomach, duodenum, liver, kidney, adrenal, and pancreas. There are many distinctive ultrastructural features among the various tumors that can be used effectively by the diagnostic electron microscopist, but it is also important to take into account the considerable overlap in fine structure that occurs among different tumors and among similar tumors from different organs. In the session on upper abdominal neoplasms, the electron microscopic characteristics of the common tumors of each viscus were reviewed before the presentation of individual case studies that incorporated original observations and illustrated some unusual entities. The selection of cases that follows is inevitably small and arbitrary, but the cases demonstrate the contribution that electron microscopy can make in the study of an upper abdominal mass and illustrate some of the similarities that can be encountered among tumors of different organs.

Malignant islet cell tumor of the pancreas with multiple hormone production and expression of CEA and CA19-9. Report of an autopsy case

An autopsy case of malignant islet cell tumor of the pancreas is presented. The patient, a 64-year-old woman showed severe hypoglycemia as the initial symptom, and hyperinsulinemia was demonstrated by laboratory examinations. Metastatic tumors in the liver were found by abdominal computed tomography. Autopsy revealed a tumor measuring 6.5 x 3 x 2 cm occupying the pancreas from the body to the tail. From the results of histological and immunohistochemical studies, this was diagnosed as a malignant islet cell tumor producing multiple hormones such as insulin, glucagon, somatostatin and pancreatic polypeptide, as well as expressing the tumor-related antigens CEA and CA19-9. These findings suggested that the tumor cells showed differentiation to both endocrine cells and pancreatic duct cells.

Ultrastructure and electron immunocytochemistry of insulin-producing B-cell tumors from transgenic mice: comparison with counterpart human tumors

This paper reports on an ultrastructural and electron-microscopic immunocytochemical study of pancreatic B cells from normal mice, pancreatic B cells and derivative tumors from transgenic mice, and tissue from human pancreatic B-cell tumors. In normal and neoplastic B cells from both species, typical immature and mature beta-granules (with spherical cores of variable density) were observed, whereas typical beta-granules with a crystalloid core were only present in human B cells (normal and tumor). A small number of atypical granules were found in distinct neoplastic cells which contained no typical beta-granules. The atypical granules were smaller (100-200 nm diameter) than typical beta-granules (250-450 nm diameter) seen in other cells. Immunoreactivity for proinsulin was localized only to immature granules, whereas insulin and C-peptide immunoreactivities were demonstrated in atypical, immature, and mature granules. In transgenic mouse and human B-cell tumors, insulin immunoreactivity was consistently weaker than the immunostaining for C-peptide. An intragranular, topographic segregation of immunoreactive C-peptide was observed in a population of transgenic tumor cells. Our results showed similarities in antigenic distribution and only slight differences in morphology between human and mouse B cells. Therefore, the transgenic mouse system may prove to be an effective model for studying mammalian B-cell tumorigenesis.

Pancreatic endocrine tumors

In this review the current state of our understanding of endocrine tumors of the pancreas is considered. It is based on the experience with a series of 365 tumors. The first part of the article focuses on origin and classification, markers, frequency, criteria of malignancy as well as general structural features of the pancreatic endocrine tumors. In the second half of the article the functioning tumors, i.e. tumors that cause hormonal syndromes, and the nonfunctioning tumors as well as the endocrine tumors associated with multiple endocrine neoplasia type 1 are dealt with in detail. Special emphasis is put on the immunocytochemical profile and the biological features of the respective tumors.

Electron microscope localisation of insulin-like immunoreactivity of conventionally processed human insulinomas

Localisation of insulin-like immunoreactivity has been studied using the immunogold staining procedure on thin sections of 6 human insulinomas, conventionally processed for electron microscopy. The labelling was restricted to the secretory granules. Depending on their morphology, these either resembled B-cell granules of human adult pancreas or belonged to the atypical (non-diagnostic) group. Within the former group, those with a crystalloid core or an amorphous dense or moderately dense core were strongly immunoreactive, whereas others, filled with a pale material, were poorly labelled. Most granules of this type were stored together within the heavily granulated cells of 3 insulinomas, presenting the classical features of clinical and biological behaviour and a typical light microscopic staining pattern. In contrast, the non-diagnostic granules, characterized by their smaller size, a very dense core and a thin halo, were mainly found within the poorly granulated cells making up the other tumours, and showed a very uneven labelling. Strongly labelled granules were found in one insulinoma that also belonged to the classical type; these were stored together with a few diagnostic granules within the same cells. Only poorly labelled atypical granules were present in two cases revealing a number of unusual features; these included moderate elevation of insulinaemia, uncertain tumour histology, as well as weak immunostaining for insulin/proinsulin and variable argyrophilia of the tumour in paraffin sections. These findings suggest that human insulinomas differ not only in storage capacity but also in their degree of granule maturation. This may involve some deficiency of either the prohormone conversion or the subsequent processing of the cleavage products.

Malignant insulinoma with metastasis to gallbladder and bone, accompanied by past history of peptic ulcer and hyperthyroidism

A case of a malignant insulinoma in a 53-year-old female is presented. In 1973, the patient underwent caudal pancreatectomy for a malignant insulinoma. Ten years later, it was discovered that the insulinoma had spread to the bones. On admission for cholecystectomy because of a gallbladder polyp and gallstones, she often experienced hypoglycemic attacks, and both calcium and glucagon provocation tests elicited marked release of insulin. Selective angiography of the common hepatic artery showed a tumor blush near the hilum of the liver. Immunohistochemical staining of the gallbladder polyp and the bone tumors proved positive for insulin. Plasma levels of insulin and prolactin were abnormally high. The patient had also been treated for a perforated duodenal ulcer and hyperthyroidism. It is concluded that this may have been a case of a multiple endocrine neoplasia.

Immunocytochemistry of normal pancreatic islets and spontaneous islet cell tumors in dogs

Immunocytochemical studies of the distribution of glucagon, gastrin, insulin, and somatostatin in normal canine pancreatic islets and 20 canine islet cell tumors were done using the peroxidase-anti-peroxidase (PAP) technique. In the normal adult canine pancreas, islets typically consisted of clusters of 20-30 cells, but smaller foci and even individual cells were identified. Alpha cells (glucagon) were often peripherally located, beta cells (insulin) were centrally located and most numerous, and delta cells (somatostatin) were the least numerous and randomly located. Both juvenile and adult canine pancreases did not stain for gastrin. Of the 20 tumors examined, 18 had positive immunoreactivity for insulin, nine for glucagon, 14 for somatostatin, and one for gastrin. Two tumors were uninterpretable due to autolysis. Three tumors were pure insulinomas, but no pure somatostatinomas, glucagonomas, or gastrinomas were identified. Most tumors and metastases had mixed positive immunoreactivity; one neoplastic cell type predominated with lesser numbers of other cell types. Metastatic sites (liver and lymph node) stained for insulin and somatostatin, only. Foci of non-neoplastic islet cell tissue (nesidioblastosis), often located at the pancreatic-mesenteric junction, stained strongly positive for insulin, glucagon, and somatostatin but not for gastrin. The tumor staining pattern did not consistently correlate with tumor function, as determined by blood glucose and serum insulin assays. The PAP technique works well on paraffin-embedded, formalin-fixed tissue using rabbit or guinea pig antisera as the primary antibody. Staining occurred on sections of paraffin blocks stored for up to 7 years.

Transgenic mouse model: a new approach for the investigation of endocrine pancreatic B-cell growth

The transformation and adaptation of pancreatic insulin-producing (B) cells has been studied in a transgenic mouse model using a panel of antisera recognising peptides and general neuroendocrine markers at both light and electron microscopical levels. Stages of tumour genesis in the transgenic mouse model from hyperplasia to neoplasia, have been compared with human B-cell tumours. A normal complement of peptide containing cells was seen in the transgenic mouse pancreas, but cells containing pro-insulin-derived peptides became more numerous as hyperplasia commenced. The transgenic mouse tumours were composed of B cells, although 30-35% of the tumours were also found to contain PP cells--a finding which is directly comparable with that in human insulin-producing tumours. NSE, 7B2 and chromogranin immunoreactivities were found in most cells from all the tumours examined. Antisera to PGP 9.5, a novel marker for elements of the neuroendocrine system, were found to stain hyperplastic and neoplastic B-cells intensely. In contrast, normal mouse B-cells did not show PGP 9.5 immunoreactivity thus it appears that PGP 9.5 is differentially expressed in transformed and/or growing mouse B-cells and hence may be used as an indicator in studies of early tumour growth.

Calcitonin-producing insulinoma. An immunohistochemical and electron microscopic study

A pancreatic endocrine tumor measuring 1.5 X 1.0 X 1.0 cm in a 67-year-old man with recurrent hypoglycemic attacks was examined by immunohistochemistry and electron microscopy. The tumor cells were relatively uniform, and almost all of them were immunoreactive to insulin. A few calcitonin-positive cells could be identified scattering in tumor cell strands, and the content of calcitonin in the tumor was 85 ng/g wet tissue. Coexistence of insulin and calcitonin in tumor cells was demonstrated by using adjacent semithin sections of the Epon-embedded material. Electron microscopically, the tumor consisted of a single type of cells with secretory granules identical to B-cell granules in the normal counterpart.