Functional Pancreatic Neuroendocrine Neoplasms: An Overview

Well-differentiated pancreatic neuroendocrine tumors (PNETs) can be non-functional or functional, e.g. insulinoma and glucagonoma. The majority of PNETs are sporadic, but PNETs also occur in hereditary syndromes, primarily multiple endocrine neoplasia type 1 (MEN1). The Knudson hypothesis stated a second, somatic hit in MEN1 as the cause of PNETs of MEN1 syndrome. In the recent years, reports on genetic somatic events in both sporadic and hereditary PNETs have emerged, providing a basis for a more detailed molecular understanding of the pathophysiology. In this systematic review and meta-analysis, we made a collation and statistical analysis of aggregated frequent genetic alterations and potential driver events in human grade G1/G2 PNETs. A systematic search was performed in concordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) reporting guidelines of 2020.A search in Pubmed for published studies using whole exome, whole genome, or targeted gene panel (+400 genes) sequencing of human G1/G2 PNETs was conducted at the 25th of September 2023. Fourteen datasets from published studies were included with data on 221 patients and 225 G1/G2 PNETs, which were divided into sporadic tumors, and hereditary tumors with pre-disposing germline variants, and tumors with unknown germline status. Further, non-functioning and functioning PNETs were distinguished into two groups for pathway evaluation. The collated genetical analyses were conducted using the 'maftools' R-package. Sporadic PNETs accounted 72.0% (162/225), hereditary PNETs 13.3% (30/225), unknown germline status 14.7% (33/225). The most frequently altered gene was MEN1, with somatic variants and copy number variations in overall 42% (95/225); hereditary PNETs (germline variations in MEN1, VHL, CHEK2, BRCA2, PTEN, CDKN1B, and/or MUTYH) 57% (16/30); sporadic PNETs 36% (58/162); unknown germline status 64% (21/33). The MEN1 point mutations/indels were distributed throughout MEN1. Overall, DAXX (16%, 37/225) and ATRX-variants (12%, 27/225) were also abundant with missense mutations clustered in mutational hotspots associated with histone binding, and translocase activity, respectively. DAXX mutations occurred more frequently in PNETs with MEN1 mutations, p<0.05. While functioning PNETs shared few variated genes, non-functioning PNETs had more recurrent variations in genes associated with the Phosphoinositide 3-kinase, Wnt, NOTCH, and Receptor Tyrosine Kinase-Ras signaling onco-pathways. The somatic genetic alterations in G1/G2 PNETs are diverse, but with distinct differences between sporadic vs. hereditary, and functional vs. non-functional PNETs. Increased understanding of the genetic alterations may lead to identification of more drivers and driver hotspots in the tumorigenesis in well-differentiated PNETs, potentially giving a basis for the identification of new drug targets. (Funded by Novo Nordisk Foundation, grant number NNF19OC0057915).

Clinical features and postoperative survival in patients with sporadic versus multiple endocrine neoplasia type 1-related pancreatic neuroendocrine tumors: An international cohort study

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the combined occurrence of parathyroid and adrenocortical tumors, and neuroendocrine tumors (NETs) of the pancreas and pituitary. The pancreatic NETs are predominantly gastrinomas and insulinomas, and the pituitary NETs are mostly prolactinomas and somatotrophinomas. We postulated that the different types of pancreatic and pituitary NETs may be partly due to differences in their proliferation rates, and we therefore assessed these in MEN1-associated tumors and gonadal tumors that developed in mice deleted for an Men1 allele (Men1(+/-)). To label proliferating cells in vivo, Men1(+/-) and wild-type (Men1(+/+)) mice were given 5-bromo-2-deoxyuridine (BrdU) in drinking water from 1-12 wk, and tissue sections were immunostained using anti-BrdU and hormone-specific antibodies. Proliferation in the tumors of Men1(+/-) mice was significantly (P < 0.001) increased when compared with the corresponding normal Men1(+/+) tissues. Pancreatic, pituitary and adrenocortical proliferation fitted first- and second-order regression lines in Men1(+/+) tissues and Men1(+/-) tumors, respectively, R(2) = 0.999. Apoptosis was similar in Men1(+/-) pancreatic, pituitary, and parathyroid tumors when compared with corresponding normal tissues, decreased in Men1(+/-) adrenocortical tumors, but increased in Men1(+/-) gonadal tumors. Mathematical modeling of NET growth rates (proliferation minus apoptosis rates) predicted that in Men1(+/-) mice, only pancreatic β-cells, pituitary lactotrophs and somatotrophs could develop into tumors within a murine lifespan. Thus, our studies demonstrate that Men1(+/-) tumors have low proliferation rates (<2%), second-order kinetics, and the higher occurrence of insulinomas, prolactinomas, and somatotrophinomas in MEN1 is consistent with a mathematical model for NET proliferation.

Multiple endocrine neoplasia type 1 (MEN1) is an inherited endocrine neoplastic syndrome associated with a greater risk of endocrine tumor development like pancreatic neuroendocrine tumors (p-NET), with different clinical characteristics from sporadic ones. This paper aims to compare clinical, hystological and morphological aspects of p-NET in patients affected from MEN1 (MEN1+) and not-affected ones (MEN1-). We performed a retrospective observational study. Data was collected between December 2010 and December 2015, including patients with a histological diagnosis of p-NET and radiological imaging. We compared clinical, histological, radiological, and prognostic aspects of MEN+ p-NET with MEN-1 p-NET. Of the 45 patients enrolled, 13 MEN1+ and 21 MEN1- cases were analyzed. Frequency of not secreting p-NETs and insulin secreting p-NETs, histopathological grades and Ki67 expression were superimposable between MEN1+ and MEN1- patients. MEN1+ pNETs are more often multicentric compared to MEN1- pNETs. Frequency of liver and nodes metastatic spread was higher in MEN1- p-NET compared to MEN1+ p-NET. Analyzing p-NET according to the disease outcome, we found that recovered and stable p-NETs in MEN1+ patients, compared to MEN1- cases, are diagnosed at lower age (p = 0.04/p = 0.002) and that are more frequently multifocal lesions (p = 0.009/p = 0.002). In our study pNETs in MEN1+ and pNETs in MEN1- don't significantly differ for prognosis but only for clinical features. p-NET stage disease and prognosis can be positively influenced by early diagnosis and screening in index patients' first-degree relatives.

Background and aims In multiple endocrine neoplasia type 1 (MEN1), endoscopic ultrasound (EUS) is used for identification and follow-up of pancreatic neuroendocrine tumors (PNETs). The role of EUS in surveillance of small ( < 20 mm) PNETs is unclear, mostly because the natural course of these lesions is largely unknown. We aimed to determine annual growth and incidence rate of small PNETs in patients with MEN1 using EUS-based surveillance. Patients and methods Linear array EUS procedures in patients with MEN1 between 2002 and 2015 were identified. Number, size, and location of PNETs were recorded. Annual growth of PNETs < 20 mm identified at the initial EUS ("prevalent" PNETs) and during follow-up ("incident" PNETs) was calculated using mixed model linear regression analysis. Results A total of 54 patients were identified and 38 patients were included. In all, 226 PNETs were identified (median size 5.0 mm, interquartile range 3.7 - 7.5) of which 124 (55 %) were prevalent and 102 (45 %) were incident PNETs. Annual incidence rate was 0.79 PNETs/year (95 % confidence interval [CI] 0.73 to 0.87). Overall growth rate was 0.10 mm/year (95 %CI 0.02 to 0.19; P = 0.01); PNETs < 10 mm (n = 198) did not grow (P = 0.23), whereas PNETs ≥ 10 mm (n = 28) grew 0.44 mm/year (95 %CI 0.10 to 0.78; P = 0.01). Prevalent PNETs grew 0.21 mm/year (95 %CI 0.10 - 0.32; P < 0.001), whereas incident PNETs did not grow (P = 0.26). Conclusions The annual growth rate of small, solid PNETs in patients with MEN1 is lower than previously thought. Surveillance intervals could probably be prolonged without compromising safety.

Pancreatic neuroendocrine tumours (PNETs) might occur as a non-familial isolated endocrinopathy or as part of a complex hereditary syndrome, such as multiple endocrine neoplasia type 1 (MEN1). MEN1 is an autosomal dominant disorder characterized by the combined occurrence of PNETs with tumours of the parathyroids and anterior pituitary. Treatments for primary PNETs include surgery. Treatments for non-resectable PNETs and metastases include biotherapy (for example, somatostatin analogues, inhibitors of receptors and monoclonal antibodies), chemotherapy and radiological therapy. All these treatments are effective for PNETs in patients without MEN1; however, there is a scarcity of clinical trials reporting the efficacy of the same treatments of PNETs in patients with MEN1. Treatment of PNETs in patients with MEN1 is challenging owing to the concomitant development of other tumours, which might have metastasized. In recent years, preclinical studies have identified potential new therapeutic targets for treating MEN1-associated neuroendocrine tumours (including PNETs), and these include epigenetic modification, the β-catenin-wingless (WNT) pathway, Hedgehog signalling, somatostatin receptors and MEN1 gene replacement therapy. This Review discusses these advances.

Pancreatic neuroendocrine tumours (PNETs) are the major source of disease-specific mortality in multiple endocrine neoplasia type 1 (MEN1) patients. Chromogranin A (CgA), pancreatic polypeptide (PP), glucagon and gastrin have some diagnostic value in sporadic PNETs, but there is very little evidence for their efficacy in diagnosing PNETs in MEN1 patients. We performed a retrospective chart review of the existing MEN1 database in our institution. One hundred and thirteen patients were eligible for diagnostic value analysis of tumour markers. Patients were excluded if measurement of tumour markers was missing, either 3 months prior to PNET diagnosis (PNET patients) or prior to abdominal imaging (non-PNET patients). Clinicopathologic characteristics and of tumour marker measurements were analysed. Of 293 confirmed MEN1 cases, 55 PNETs and 58 non-PNETs met inclusion criteria. The area under the curve (AUC) for CgA, PP, glucagon and gastrin in MEN1 cases was 59·5%, 64·1%, 77·0% and 75·9%, respectively. The AUC for the combination of CgA, PP and gastrin was 59·6%. PP, but not CgA, glucagon or gastrin was significantly associated with both age and PNET functional status (P = 0·0485 and 0·0188, respectively). No markers were significantly associated with sex, PNET size, tumour number, tumour location, American Joint Committee on Cancer (AJCC) stage, presence of lymph node metastasis, lymphovascular invasion or overall survival. CgA values were not significantly lower following PNET resection than pre-operatively (P = 0·554). The value of blood markers for diagnosing PNETs in MEN1 patients is relatively low, even when used in combination.

Pancreatic neuroendocrine tumors (PNETs) are rare, indolent tumors that may occur sporadically or develop in association with well-recognized hereditary syndromes, particularly multiple endocrine neoplasia type 1 (MEN-1). We previously demonstrated that the hedgehog (HH) signaling pathway was aberrantly up-regulated in a mouse model that phenocopies the human MEN-1 syndrome, Men1l/l;RipCre, and that inhibition of this pathway suppresses MEN-1 tumor cell proliferation. We hypothesized that the HH signaling pathway is similarly upregulated in human PNETs. We performed immunohistochemical (IHC) staining for PTCH1 in human fresh and archival PNET specimens to examine whether human sporadic and MEN-1-associated PNETs revealed similar abnormalities as in our mouse model and correlated the results with clinical and demographic factors of the study cohort. PTCH1 staining was positive in 12 of 22 PNET patients (55%). Four of 5 MEN-1 patients stained for PTCH1 (p = 0.32 as compared with sporadic disease patients). Nine of 16 patients with metastatic disease stained for PTCH1 as compared with zero of 3 with localized disease only (p = 0.21). No demographic or clinical features appeared to be predictive of PTCH 1 positivity and PTCH 1 positivity per se was not predictive of clinical outcome. PTCH1, a marker of HH pathway up regulation, is detectable in both primary and metastatic tumors in more than 50% of PNET patients. Although no clinical or demographic factors predict PTCH1 positivity and PTCH1 positivity does not predict clinical outcome, the frequency of expression alone indicates that perturbation of this pathway with agents such as Vismodegib, an inhibitor of Smoothened (SMO), should be examined in future clinical trials.

Genotype-phenotype pancreatic neuroendocrine tumor relationship in multiple endocrine neoplasia type 1 patients: A 23-year experience at a single institution

Although neuroendocrine tumors (NETs) are rare, the number of patients with NET is increasing. However, in Japan, there have been no epidemiological studies on NET since 2005; thus, the prevalence of NET remains unknown. We reported the epidemiology of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) [pancreatic neuroendocrine tumors (PNETs) and gastrointestinal neuroendocrine tumors (GI-NETs)] in Japan in 2005. Here, we conducted the second nationwide survey on patients with GEP-NETs who received treatment in 2010. A total of 3,379 patients received treatment for PNETs in 2010, representing a 1.2-fold increase in the number of patients from 2005 to 2010. The prevalence was estimated to be 2.69/100,000, with an annual onset incidence of 1.27/100,000 in 2010. Non-functioning tumor (NF)-PNETs comprised 65.5% of cases followed by insulinoma (20.9%) and gastrinoma (8.2%). Interestingly, the number of patients with NF-PNETs increased ~1.8 fold since 2005. A total of 19.9% of patients exhibited distant metastasis at initial diagnosis; 4.3% had complications with multiple endocrine neoplasia type 1 (MEN-1), and only 4.0% had NF-PNETs associated with MEN-1. Meanwhile, an estimated 8,088 patients received treatment for GI-NETs, representing a ~1.8-fold increase since 2005. The prevalence was estimated to be 6.42/100,000, with an annual onset incidence of 3.51/100,000. The locations of GI-NETs varied: foregut, 26.1%; midgut, 3.6%; and hindgut, 70.3%. Distant metastasis and complications with MEN-1 were observed in 6.0 and 0.42% at initial diagnosis, respectively. The frequency of carcinoid syndrome in patients with GI-NETs was 3.2%. We clarified the epidemiological changes in GEP-NETs from 2005 to 2010 in Japan.

Pasireotide, a somatostatin analog, is reported to have anti-proliferative effects in neuroendocrine tumors (NETs). We therefore assessed the efficacy of pasireotide for treating pancreatic and pituitary NETs that develop in a mouse model of multiple endocrine neoplasia type 1 (MEN1). Men1+/− mice were treated from age 12 mo with 40 mg/kg pasireotide long-acting release formulation, or PBS, intramuscularly monthly for 9 mo. The Men1+/− mice had magnetic resonance imaging at 12 and 21 mo, and from 20 mo oral 5-bromo-2-deoxyuridine for 1 mo, to assess tumor development and proliferation, respectively. NETs were collected at age 21 mo, and proliferation and apoptosis assessed by immunohistochemistry and TUNEL assays, respectively. Pasireotide-treated Men1+/− mice had increased survival (pasireotide, 80.9% vs PBS, 65.2%; P < .05), with fewer mice developing pancreatic NETs (pasireotide, 86.9% vs PBS, 96.9%; P < .05) and smaller increases in pituitary NET volumes (pre-treated vs post-treated, 0.803 ± 0.058 mm3 vs 2.872 ± 0.728 mm3 [pasireotide] compared with 0.844 ± 0.066 mm3 vs 8.847 ±1.948 mm3 [PBS]; P < .01). In addition, pasireotide-treated mice had fewer pancreatic NETs compared with PBS-treated mice (2.36 ± 0.25 vs 3.72 ± 0.32, respectively; P < .001), with decreased proliferation in pancreatic NETs (pasireotide, 0.35 ± 0.03% vs PBS, 0.78 ± 0.08%; P < .0001) and pituitary NETs (pasireotide, 0.73 ±0.07% vs PBS, 1.81 ± 0.15%; P < .0001), but increased apoptosis in pancreatic NETs (pasireotide, 0.42 ± 0.05% vs PBS, 0.19 ± 0.03%; P < .001) and pituitary NETs (pasireotide, 14.75 ± 1.58% vs PBS, 2.35 ± 0.44%; P < .001). Thus, pasireotide increased survival and inhibited pancreatic and pituitary NET growth, thereby indicating its potential as an anti-proliferative and pro-apoptotic therapy.

Pancreatic neuroendocrine tumours (PNETs) are the most common cause of death in patients with multiple endocrine neoplasia type 1 (MEN1). Women have been shown to have improved survival, which may suggest a possible protective effect of female sex hormones. The aim of this study was to evaluate the relationship between estrogen exposure and PNET tumourigenesis, tumour growth and survival in female MEN1 patients with these tumours. We performed a retrospective chart review of the existing MEN1 database in our institution. Detailed information about female patients' menstrual and reproductive history, and PNET clinicopathologic characteristics was collected. Questionnaires regarding estrogen exposure were used to collect information that was missing in the database. Of 293 confirmed MEN1 cases, 141 women met the inclusion criteria. We used measures of cumulative estrogen exposure time (CEET), parity, live birth pregnancies and bilateral oophorectomy to estimate estrogen exposure. There was no significant association between CEET and time to PNET diagnosis (hazard ratio=0·966, P=0·380). For the correlation between estrogen exposure and PNET type, size, numbers, distant metastasis, lymph node metastasis, lymphovascular invasion, AJCC (American Joint Committee on Cancer) stage and overall survival, only CEET was significantly correlated with PNET size (P=0·043). In female patients with MEN1, estrogen exposure may inhibit PNET growth. A demonstrable protective effect against PNET tumourigenesis, tumour growth and survival of patients with these tumours may require a larger cohort.

Foregut-derived neuroendocrine (NE) tumors occur sporadically or in association with multiple endocrine neoplasia type 1 (MEN1) syndrome. Thirty-nine sporadic NE tumors of foregut derivation (six thymic, 21 bronchial, three gastric, and nine pancreatic tumors) as well as two hindgut-derived rectal carcinoids for somatic MEN1 gene mutation were analyzed by direct sequencing analysis. Five tumors showed mutations: nonsense mutations (Q393X and R98X) in thymic and pancreatic NE tumors, respectively, a 4 b.p. deletion (357del4) in a gastric NE carcinoma, and missense mutations (D172Y and S178Y) in pancreatic NE tumors. No mutation was identified in pulmonary or rectal NE tumors. In a patient with a pancreatic NE tumor (D172Y), the corresponding germline DNA showed the same mutation, suggesting that sporadic MEN1 syndrome was masked in this case. Somatic MEN1 gene mutations and deletions may play a crucial role in the tumorigenesis of a subset of foregut-derived NE tumors. Sporadic MEN1 syndrome may occur as a sporadic NE tumor of the pancreas.

Although in most cases insulinomas are small, benign, sporadic tumours, they can also be associated with hereditary syndromes, most commonly multiple endocrine neoplasia type 1 (MEN-1). Such a diagnosis significantly affects patient management. The objective was to elucidate the clinical differences between sporadic and MEN-1-linked insulinoma. Comparison of clinical and histopathological characteristics, types of surgery, and outcomes of patients with sporadic and MEN-1-related insulinoma diagnosed between 2015 and 2022. There were 17 cases of insulinomas that underwent MEN-1 genetic testing (10 women and 7 men). In 7 cases, the mutation in the menin gene was confirmed. The median age at the time of diagnosis of sporadic insulinoma related to MEN-1 was 69 years (range 29-87) and 31.5 years (16-47), respectively. Primary hyperparathyroidism (PHP) was found in 6 of 7 patients with MEN-1-related insulinoma, while in none of the patients without MEN-1 mutations. Multifocal pancreatic NETs were found in 3 patients with MEN-1 syndrome, while in all sporadic cases there was a single pancreatic tumour. Two patients with insulinoma related to MEN-1 had a positive familial history of MEN-1-related diseases, while none with sporadic form. Dissemination at diagnosis was found in 4 cases, including 3 patients with insulinoma related to MEN-1-related insulinoma. Patients with sporadic and MEN-1-related insulinoma did not differ in tumour size, Ki-67 proliferation index, and outcome. Of all the features evaluated, only the multifocal nature of pancreatic neuroendocrine tumour (PanNET) lesions and a positive family history differentiated between patients with sporadic and MEN-1-related insulinomas. An age of insulinoma diagnosis of less than 30 years may be a strong indicator of an increased risk of MEN-1 syndrome.

Pancreatic neuroendocrine tumors (PanNETs) and lung NETs (LNETs) represent a rare but clinically significant subgroup of neoplasms. While the majority is sporadic, approximately 17% of PanNETs and a subset of LNETs develop in the context of monogenic familial tumor syndromes, especially multiple endocrine neoplasia type 1 (MEN1) syndrome. Other inherited syndromes associated with PanNETs include MEN4, von Hippel-Lindau (VHL) syndrome, neurofibromatosis type 1 (NF1), and tuberous sclerosis complex (TSC). These syndromes are highly penetrant and their clinical manifestations may vary even among members of the same family. They are attributed to genetic mutations involving key molecular pathways regulating cell growth, differentiation, and angiogenesis. Pancreatic NETs in hereditary syndromes are often multiple, develop at a younger age compared to sporadic tumors, and are associated with endocrine and nonendocrine tumors derived from multiple organs. Lung NETs are not as common as PanNETs and are mostly encountered in MEN1 syndrome and include typical and atypical lung carcinoids. Early detection of PanNETs and LNETs related to inherited syndromes is crucial, and specific follow-up protocols need to be employed to optimize diagnosis and management. Genetic screening is recommended in childhood, and diagnostic screening starts often in adolescence, even in asymptomatic mutation carriers. Optimal management and therapeutic decisions should be made in the context of a multidisciplinary team in specialized centers, whereas specific biomarkers aiming to identify patients denoted to follow a more aggressive course need to be developed.