Metastatic Patterns of Duodenopancreatic Neuroendocrine Tumors in Patients With Multiple Endocrine Neoplasia Type 1

Patients with multiple endocrine neoplasia 1 syndrome (MEN1) often develop multifocal duodenopancreatic neuroendocrine tumors (dpNETs). Nonfunctional pancreatic neuroendocrine tumors (PanNETs) and duodenal gastrinomas are the most frequent origins of metastasis. Current guidelines recommend surgery based on tumor functionality, size ≥2 cm, grade or presence of lymph node metastases. However, in case of multiple primary tumors it is often unknown which specific tumor metastasized. This study aims to unravel the relationship between primary dpNETs and metastases in patients with MEN1 by studying endocrine differentiation. First, it was shown that expression of the endocrine differentiation markers ARX and PDX1 was concordant in 18 unifocal sporadic neuroendocrine tumors (NETs) and matched metastases. Thereafter, ARX, PDX1, Ki67 and gastrin expression, and the presence of alternative lengthening of telomeres were determined in 137 microscopic and macroscopic dpNETs and 36 matched metastases in 10 patients with MEN1. ARX and PDX1 H-score clustering was performed to infer relatedness. For patients with multiple metastases, similar intrametastases transcription factor expression suggests that most metastases (29/32) originated from a single NET of origin, while few patients may have multiple metastatic primary NETs. In 6 patients with MEN1 and hypergastrinemia, periduodenopancreatic lymph node metastases expressed gastrin, and clustered with minute duodenal gastrinomas, not with larger PanNETs. PanNET metastases often clustered with high grade or alternative lengthening of telomeres-positive primary tumors. In conclusion, for patients with MEN1-related hypergastrinemia and PanNETs, a duodenal origin of periduodenopancreatic lymph node metastases should be considered, even when current conventional and functional imaging studies do not reveal duodenal tumors preoperatively.

Asymptomatic children with multiple endocrine neoplasia type 1 mutations may harbor nonfunctioning pancreatic neuroendocrine tumors

CONTEXT

Multiple endocrine neoplasia type 1 (MEN1) is characterized by the occurrence of parathyroid, pituitary, and pancreatic tumors. MEN1, an autosomal dominant disorder, has a high degree of penetrance, such that more than 95% of patients develop clinical manifestations by the fifth decade, although this is lower at approximately 50% by age 20 yr. However, the lower penetrance in the younger group, which is based on detecting hormone-secreting tumors, may be an underestimate because patients may have nonfunctioning tumors and be asymptomatic.

OBJECTIVE

The aim of the study was to evaluate the occurrence of nonfunctioning pancreatic neuroendocrine tumors in asymptomatic children with MEN1.

PATIENTS

Twelve asymptomatic Northern European children, aged 6 to 16 yr, who were known to have MEN1 mutations were studied.

RESULTS

Two asymptomatic children, who were aged 12 and 14 yr, had normal plasma fasting gastrointestinal hormones and were found to have nonfunctioning pancreatic neuroendocrine tumors that were more than 2 cm in size. Surgery and immunostaining revealed that the tumors did not have significant expression of gastrointestinal hormones but did contain chromogranin A and synaptophysin, features consistent with those of nonfunctioning pancreatic neuroendocrine tumors. The tumors had a loss of menin expression. The 14 yr old also had primary hyperparathyroidism and a microprolactinoma, and the 12 yr old had a nonfunctioning pituitary microadenoma. Three other children had primary hyperparathyroidism and a microprolactinoma.

CONCLUSION

Nonfunctioning pancreatic neuroendocrine tumors may occur in asymptomatic children with MEN1 mutations, and screening for such enteropancreatic tumors in MEN1 children should be considered earlier than the age of 20 yr, as is currently recommended by the international guidelines.

Broad tumor spectrum in a mouse model of multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1) is an inherited cancer predisposition syndrome typified by development of tumors in parathyroid, pituitary and endocrine pancreas, as well as less common sites including both endocrine and nonendocrine organs. Deletion or mutation of the tumor suppressor gene MEN1 on chromosome 11 has been identified in many cases of MEN1 as well as in sporadic tumors. The molecular biology of menin, the protein encoded by MEN1, remains poorly understood. Here we describe a mouse model of MEN1 in which tumors were seen in pancreatic islets, pituitary, thyroid and parathyroid, adrenal glands, testes and ovaries. The observed tumor spectrum therefore includes types commonly seen in MEN1 patients and additional types. Pancreatic pathology was most common, evident in over 80% of animals, while other tumor types developed with lower frequency and generally later onset. Tumors of multiple endocrine organs were observed frequently, but progression to carcinoma and metastasis were not evident. Tumors in all sites showed loss of heterozygosity at the Men1 locus, though the frequency in testicular tumors was only 36%, indicating that a different molecular mechanism of tumorigenesis occurs in those Leydig tumors that do not show loss of the normal Men1 allele. Menin expression was below the level of detection in ovary, thyroid and testis, but loss of nuclear menin immunoreactivity was observed uniformly in all pancreatic islet adenomas and in some hyperplastic islet cells, suggesting that complete loss of Men1 is a critical point in islet tumor progression in this model.

Co-expression of ghrelin and its receptor in pancreatic endocrine tumours

OBJECTIVE

Expression of ghrelin has been reported in pancreatic endocrine tumours, but data on ghrelin receptor protein expression are lacking. The aim of this study was to examine the ghrelin receptor, as well as ghrelin, in a selected series of these tumours, including multiple endocrine neoplasia 1 (MEN1) associated tumours, and to correlate data with clinical features including body mass index.

DESIGN

Immunohistochemical detection of ghrelin and its receptor was performed on frozen tissue from 31 tumours: 9 MEN1 and 22 sporadic. Twenty tumours were analysed by quantitative PCR. Plasma ghrelin was assessed in 26 patients.

RESULTS

Twenty-one (68%) of 31 tumours showed immunoreactivity for ghrelin (8/9 MEN1) and 19/20 expressed ghrelin mRNA. Ghrelin receptor protein was detected in 21/30 (70%) tumours (4/8 MEN1), and mRNA was detected in all analysed tumours. Insulinomas had significantly higher levels of receptor mRNA than other tumours. Five patients had elevated plasma ghrelin (> 2 SD above the control group mean). No significant difference in mean plasma ghrelin levels was found between patients (908 +/- 569 ng/l) and controls (952 +/- 164 ng/l). Mean BMI was 24.3 kg/m(2). There was no association between ghrelin or receptor expression and survival.

CONCLUSIONS

We report the first immunohistochemical data on expression of the ghrelin receptor in pancreatic endocrine tumours: 70% of tumours in our material. Concomitant ghrelin and receptor expression was seen in 50% of tumours, indicating an autocrine loop. Ghrelin was expressed in 68% of tumours (8/9 MEN1). Despite frequent ghrelin expression, elevated circulating ghrelin is rare in these patients.

Intracytoplasmic inclusions (including the so-called "rhabdoid" phenotype) in pancreatic endocrine tumors

The cytoplasm of pancreatic endocrine tumors (PET) can show a diverse range of appearances from clear, to oncocytic, to intracellular mucin accumulation, and the presence of intracytoplasmic inclusions. Intracytoplasmic eosinophilic inclusions can vary morphologically and the spectrum ranges from small, dot-like hyaline inclusions, to deeply acidophilic/eosinophilic ones that occupy almost the whole cytoplasm and displace the nucleus eccentrically: the so-called "rhabdoid" phenotype. The aim of this study was to analyze the frequency, morphology, behavior, and relationship to clinicopathological features of large intracytoplasmic inclusions, including the rhabdoid phenotype, in a large number of PET. The morphological features of 84 cases were assessed for the presence of large, globular intracytoplasmic inclusions. Fourteen of 84 cases contained intracytoplasmic inclusions with 5 cases containing cells conforming to the characteristic rhabdoid morphology. The remaining nine cases showed pale intracytoplasmic inclusions. Four of the five cases with rhabdoid cells had spread to lymph nodes and/or peripancreatic fatty tissue. This study confirms that a spectrum of large intracytoplasmic inclusions is encountered in PET, ranging from lightly eosinophilic intracytoplasmic globules to the more typical rhabdoid phenotype (deeply eosinophilic inclusions). This phenotype, in particular the rhabdoid cells, is worthy of attention as a proportion may show lymphovascular invasion with evidence of metastasis at the time of presentation, irrespective of size, mitotic rates, or necrosis.

Valosin-containing protein (p97) and Ki-67 expression is a useful marker in detecting malignant behavior of pancreatic endocrine neoplasms

OBJECTIVE

To determine the prognostic value of valosin-containing protein (VCP) expression and the Ki-67 labeling index (LI) in pancreatic endocrine neoplasms (PENs), the present analysis was employed.

METHODS

The Ki-67 LI and VCP expression at the mRNA and protein level were evaluated in 32 patients (12 male and 20 female) with PENs aged from 22 to 73 years (median 49 years). VCP staining intensity in tumor cells was categorized as weaker (level 1) or equal to stronger (level 2) compared to nontumorous islet cells. Ki-67 LI was divided into two categories: level 1, Ki-67 LI < 5%, and level 2, > or = 5%.

RESULTS

Five cases (15.6%) showed level 1 and 25 (84.4%) level 2 VCP expression by immunohistochemistry. A significant association was observed between VCP expression and the malignant behavior of PENs (p < 0.01). All level 1 VCP tumors were benign PENs. Quantitative reverse transcription polymerase chain reaction analysis showed higher VCP mRNA expression in malignant PENs (n = 5) than benign cases (n = 5) (p < 0.05). For Ki-67 LI, 28 cases (87.5%) showed level 1 and 4 (12.5%) level 2 expression. All patients with level 2 Ki-67 LI had metastasis.

CONCLUSION

VCP expression analysis and Ki-67 LI are useful prognosticators for PENs.

Ectopic growth hormone-releasing hormone secretion by thymic carcinoid tumour

The case of a 33-year-old-woman with Multiple Endocrine Neoplasia Type 1 (MEN1) syndrome and acromegaly due to ectopic growth hormone-releasing hormone (GHRH) secretion by a thymic carcinoid tumour is reported. Immunohistochemistry revealed positive immunoreactivity for GHRH, vasoactive intestinal polypeptide, somatostatin and alpha-subunit in the tumour cells. A previously undescribed new germ line mutation of the MEN1 protein gene was revealed.

Differential expression of menin in various adrenal tumors. The role of menin in adrenal tumors

BACKGROUND

Adrenocortical tumors occur as sporadic tumors, as part of the multiple endocrine neoplasia type 1 (MEN1) syndrome, or as part of other hereditary disorders. MEN1 is a tumor suppressor gene located on chromosome 11q13 that encodes a 610-amino acid protein called menin, and plays an important role in the development of MEN1 syndrome. Recent reports indicate that heterozygous germline mutations of this gene are responsible for the disease onset of MEN1.

METHODS

To investigate the role of menin in sporadic adrenocortical tumors, the authors examined a series of adrenocortical adenoma cases and a single case of carcinoma and adrenomedulary tumors with the corresponding adjacent tumor tissues using reverse transcriptase-polymerase chain reaction (RT-PCR) for menin mRNA and Western blot analysis for menin protein. Both RNA and protein from these tumors were applied to RT-PCR and Western blot analysis, respectively, although they are not truly quantitative. Primers for RT-PCR were designed to amplify the sequence between exons 2 and 3 of the MEN1 gene. A specific antibody against menin was generated in guinea pigs immunized with the recombinant peptide from the amino acid residues 443-535 of menin made by using glutathione-S-transferase gene fusion.

RESULTS

Based on the results of RT-PCR and Western blot analysis, both MEN1 mRNA and menin protein appeared to be highly expressed in Cushing syndrome resulting from adrenocortical adenomas and carcinoma. However, their expression was found to be greatly decreased in primary aldosteronism compared with their expression in Cushing syndrome. Although weak expression of MEN1 mRNA also was detected in pheochromocytoma on RT-PCR, menin expression was not detected in any case of pheochromocytoma by Western blot analysis, possibly due to the lower sensitivity of this assay compared with RT-PCR. Neither MEN1 mRNA nor menin protein was detected in any of the corresponding adjacent tumor tissues examined.

CONCLUSIONS

The findings of the current study indicate that menin expression appears to be up-regulated in Cushing syndrome, suggesting that adrenocortical proliferation might be one of the primary lesions in the MEN1 syndrome in which menin might play a significant role in some specific cellular functions.

Presence of somatostatin receptors negatively coupled to adenylate cyclase in ectopic growth hormone-releasing hormone- and alpha-subunit-secreting tumors from acromegalic patients responsive to octreotide

The functional study of SRIH receptors was performed in ectopic GHRH-secreting tumors from two patients with acromegaly; patient 1 presented with multiple endocrine neoplasia type 1 with GHRH- and insulin-secreting pancreatic tumors, and patient 2 presented with a multihormone-secreting carcinoid tumor (including GHRH and alpha-subunit secretion, as demonstrated by clinical and immunohistochemical studies). In both cases, plasma GH levels were responsive to octreotide. In patient 2, plasma GHRH and alpha-subunit levels were responsive to octreotide. In vitro perifusion studies of a tumor fragment from patient 1 also showed inhibition of GHRH secretion by SRIH. A high density of specific SRIH-binding sites was visualized by autoradiography in GHRH tumors from both patients. SRIH specific binding was much higher in the GHRH tumors (6.6-8.4 fmol/surface unit) than in the insulinoma (1.9 fmol/surface unit). The binding inhibition constant (IC50) was in the nanomolar range (0.9-3 nmol/L) in the GHRH tumors. SRIH-14 inhibited forskolin-stimulated adenylate cyclase in the GHRH tumors from both patients, but not in the insulinoma. The functional SRIH receptors negatively coupled to adenylate cyclase present in ectopic GHRH-secreting tumors mediate the inhibitory effect of octreotide on GHRH secretion and on previously underrecognized ectopic alpha-subunit secretion from carcinoid tumors.