Pancreatic neuroendocrine tumors:Are tumors smaller than 2 cm truly indolent?

BACKGROUND Pancreatic neuroendocrine tumors(PNETs)are relatively rare but rank as the second most common pancreatic neoplasm.They can be functional,causing early metabolic disturbances due to hormone secretion,or non-functional and diagnosed later based on tumor size-related symptoms.Recent diagnoses of PNETs under 2 cm in size have sparked debates about their management;some practitioners advocate for surgical removal and others suggest observation due to the tumors’lower potential for malignancy.However,it is unclear whether managing these small tumors expectantly is truly safe.AIM To evaluate poor prognostic factors in PNETs based on tumor size(>2 cm or<2 cm)in surgically treated patients.METHODS This cohort study included 64 patients with PNETs who underwent surgical resection between 2006 and 2019 at a high-complexity reference hospital in Medellín,Colombia.To assess patient survival,quarterly follow-ups were conducted during the first year after surgery,followed by semi-annual con-sultations at the hospital's hepatobiliary surgery department.Qualitative variables were described using absolute and relative frequencies,and quantitative variables were expressed using measures of central tendency and their corresponding measures of dispersion.RESULTS The presence of lymph node involvement,neural involvement,and lymphovascular invasion were all associated with an increased risk of mortality,with hazard ratios of 5.68(95%CI:1.26–25.61,P=0.024),6.44(95%CI:1.43–28.93,P=0.015),and 24.87(95%CI:2.98–207.19,P=0.003),respectively.Neural involvement and lymphovascular invasion were present in tumors smaller than 2 cm in diameter and those larger than 2 cm in diameter.The recurrence rates between the two tumor groups were furthermore similar:18.2%for tumors smaller than 2 cm and 21.4%for tumors larger than 2 cm.Patient survival was additionally comparable between the two tumor groups.CONCLUSION Tumor size does not dictate prognosis;lymph node and lymphovascular involvement affect mortality,which high-lights that histopathological factors-rather than tumor size-may play a role in management.

Advancements in medical treatment for pancreatic neuroendocrine tumors:A beacon of hope

This editorial highlights the remarkable advancements in medical treatment strategies for pancreatic neuroendocrine tumors(pan-NETs),emphasizing tailored approaches for specific subtypes.Cytoreductive surgery and somatostatin analogs(SSAs)play pivotal roles in managing tumors,while palliative options such as molecular targeted therapy,peptide receptor radionuclide therapy,and chemotherapy are reserved for SSA-refractory patients.Gastrinomas,insul-inomas,glucagonomas,carcinoid tumors and VIPomas necessitate distinct thera-peutic strategies.Understanding the genetic basis of pan-NETs and exploring immunotherapies could lead to promising avenues for future research.This review underscores the evolving landscape of pan-NET treatment,offering renewed hope and improved outcomes for patients facing this complex disease.

Metformin and pancreatic neuroendocrine tumors:A systematic review and meta-analysis

BACKGROUND Most patients with advanced pancreatic neuroendocrine tumors(pNETs)die due to tumor progression.Therefore,identifying new therapies with low toxicity and good tolerability to use concomitantly with the established pNET treatment is relevant.In this perspective,metformin is emerging as a molecule of interest.Retrospective studies have described metformin,a widely used agent for the treatment of patients with type 2 diabetes mellitus(T2DM),to be effective in modulating different tumor-related events,including cancer incidence,recurrence and survival by inhibiting mTOR phosphorylation.This systematic review evaluates the role of T2DM and metformin in the insurgence and post-treatment outcomes in patients with pNET.AIM To systematically analyze and summarize evidence related to the diagnostic and prognostic value of T2DM and metformin for predicting the insurgence and posttreatment outcomes of pNET.METHODS A systematic review of the published literature was undertaken,focusing on the role of T2DM and metformin in insurgence and prognosis of pNET,measured through outcomes of tumor-free survival(TFS),overall survival and progression free survival.RESULTS A total of 13 studies(5674 patients)were included in this review.Analysis of 809 pNET cases from five retrospective studies(low study heterogeneity with I^(2)=0%)confirms the correlation between T2DM and insurgence of pNET(OR=2.13,95%CI=1.56-4.55;P<0.001).The pooled data from 1174 pNET patients showed the correlation between T2DM and post-treatment TFS in pNET patients(hazard ratio=1.84,95%CI=0.78-2.90;P<0.001).The study heterogeneity was intermediate,with I^(2)=51%.A few studies limited the possibility of performing pooled analysis in the setting of metformin;therefore,results were heterogeneous,with no statistical relevance to the use of this drug in the diagnosis and prognosis of pNET.CONCLUSION T2DM represents a risk factor for the insurgence of pNET and is a significant predictor of poor post-treatment TFS of pNET patients.Unfortunately,a few studies with heterogeneous results limited the possibility of exploring the effect of metformin in the diagnosis and prognosis of pNET.

Prediction of the lymphatic,microvascular,and perineural invasion of pancreatic neuroendocrine tumors using preoperative magnetic resonance imaging

BACKGROUND Significant correlation between lymphatic,microvascular,and perineural invasion(LMPI)and the prognosis of pancreatic neuroendocrine tumors(PENTs)was confirmed by previous studies.There was no previous study reported the relationship between magnetic resonance imaging(MRI)parameters and LMPI.AIM To determine the feasibility of using preoperative MRI of the pancreas to predict LMPI in patients with non-functioning PENTs(NFPNETs).METHODS A total of 61 patients with NFPNETs who underwent MRI scans and lymphadenectomy from May 2011 to June 2018 were included in this retrospective study.The patients were divided into group 1(n=34,LMPI negative)and group 2(n=27,LMPI positive).The clinical characteristics and qualitative MRI features were collected.In order to predict LMPI status in NF-PNETs,a multivariate logistic regression model was constructed.Diagnostic performance was evaluated by calculating the receiver operator characteristic(ROC)curve with area under ROC,sensitivity,specificity,positive predictive value(PPV),negative predictive value(NPV)and accuracy.RESULTS There were significant differences in the lymph node metastasis stage,tumor grade,neuron-specific enolase levels,tumor margin,main pancreatic ductal dilatation,common bile duct dilatation,enhancement pattern,vascular and adjacent tissue involvement,synchronous liver metastases,the long axis of the largest lymph node,the short axis of the largest lymph node,number of the lymph nodes with short axis>5 or 10 mm,and tumor volume between two groups(P<0.05).Multivariate analysis showed that tumor margin(odds ratio=11.523,P<0.001)was a predictive factor for LMPI of NF-PNETs.The area under the receiver value for the predictive performance of combined predictive factors was 0.855.The sensitivity,specificity,PPV,NPV and accuracy of the model were 48.1%(14/27),97.1%(33/34),97.1%(13/14),70.2%(33/47)and 0.754,respectively.CONCLUSION Using preoperative MRI,ill-defined tumor margins can effectively predict LMPI in patients with NF-PNETs.

Non-functioning pancreatic neuroendocrine tumors: Surgery or observation?

Incidentally detected, sporadic, nonfunctional pancreatic neuroendocrine tumors are increasingly diagnosed on imaging studies performed for unrelated purposes. Although their resection is usually recommended, controversy still exists regarding their optimal management, due to their highly variable and difficult to predict biologic behavior. Recently, several studies and guidelines advocated an expectant management approach in small size, low grade, incidentally diagnosed nonfunctional pancreatic neuroendocrine tumors. The aim of this study is to review and summarize the available literature addressing nonfunctional pancreatic neuroendocrine tumors, with an emphasis on surgical management controversies.

Diagnostic accuracy of endoscopic ultrasound in pancreatic neuroendocrine tumors: A systematic review and meta analysis

AIM: To detect pancreatic neuroendocrine tumors (PNETs) has been varied. This study is undertaken to evaluate the accuracy of endoscopic ultrasound (EUS) in detecting PNETs.METHODS: Only EUS studies confirmed by surgery or appropriate follow-up were selected. Articles were searched in Medline, Ovid journals, Medline nonindexed citations, and Cochrane Central Register of Controlled Trials and Database of Systematic Reviews. Pooling was conducted by both fixed and random effects model). RESULTS: Initial search identified 2610 reference articles, of these 140 relevant articles were selected and reviewed. Data was extracted from 13 studies (n = 456) which met the inclusion criteria. Pooled sensitivity of EUS in detecting a PNETs was 87.2% (95%CI: 82.2-91.2). EUS had a pooled specificity of 98.0% (95%CI: 94.3-99.6). The positive likelihood ratio of EUS was 11.1 (95%CI: 5.34-22.8) and negative likelihood ratio was 0.17 (95%CI: 0.13-0.24). The diagnostic odds ratio, the odds of having anatomic PNETs in positive as compared to negative EUS studies was 94.7 (95%CI: 37.9-236.1). Begg-Mazumdar bias indicator for publication bias gave a Kendall's tau value of 0.31 (P = 0.16), indication no publication bias. The P for χ2 heterogeneity for all the pooled accuracy estimates was > 0.10. CONCLUSION: EUS has excellent sensitivity and specificity to detect PNETs. EUS should be strongly considered for evaluation of PNETs.

Recent standardization of treatment strategy for pancreatic neuroendocrine tumors

Recent advances in localization techniques,such as the selective arterial secretagogue injection test(SASI test) and somatostatin receptor scintigraphy have promoted curative resection surgery for patients with pancreatic neuroendocrine tumors(PNET).For patients with sporadic functioning PNET,curative resection surgery has been established by localization with the SASI test using secretin or calcium.For curative resection of functioning PNET associated with multiple endocrine neoplasia type 1(MEN 1) which are usually multiple and sometimes numerous,resection surgery of the pancreas and/or the duodenum has to be performed based on localization by the SASI test.As resection surgery of PNET has increased,several important pathological features of PNET have been revealed.For example,in patients with Zollinger-Ellison syndrome(ZES),duodenal gastrinoma has been detected more frequently than pancreatic gastrinoma,and in patients with MEN 1 and ZES,gastrinomas have been located mostly in the duodenum,and pancreatic gastrinoma has been found to co-exist in 13% of patients.Nonfunctioning PNET in patients with MEN 1 becomes metastatic to the liver when it is more than 1 cm in diameter and should be resected after careful observation.The most important prognos-tic factor in patients with PNET is the development of hepatic metastases.The treatment strategy for hepatic metastases of PNET has not been established and aggressive resection with chemotherapy and trans-arterial chemoembolization have been performed with significant benefit.The usefulness of octreotide treatment and other molecular targeting agents are currently being assessed.

Laparoscopic resection of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors(PNETs)are a rare heterogeneous group of endocrine neoplasms.Surgery remains the best curative option for this type of tumor.Over the past two decades,with the development of laparoscopic pancreatic surgery,an increasingly larger number of PNET resections are being performed by these minimally-invasive techniques.In this review article,the various laparoscopic surgical options for the excision of PNETs are discussed.In addition,a summary of the literature describing the outcome of these treatment modalities is presented.

Pancreatic neuroendocrine tumors:A review of serum biomarkers,staging,and management

Pancreatic neuroendocrine tumors(pNETs)are a heterogeneous group of tumors with complicated treatment options that depend on pathological grading,clinical staging,and presence of symptoms related to hormonal secretion.With regard to diagnosis,remarkable advances have been made:Chromogranin A is recommended as a general marker for pNETs.But other new biomarker modalities,like circulating tumor cells,multiple transcript analysis,microRNA profile,and cytokines,should be clarified in future investigations before clinical application.Therefore,the currently available serum biomarkers are insufficient for diagnosis,but reasonably acceptable in evaluating the prognosis of and response to treatments during follow-up of pNETs.Surgical resection is still the only curative therapeutic option for localized pNETs.However,a debulking operation has also been proven to be effective for controlling the disease.As for drug therapy,steroids and somatostatin analogues are the first-line therapy for those with positive expression of somatostatin receptor,while everolimus and sunitinib represent important progress for the treatment of patients with advanced pNETs.Great progress has been achieved in the combination of systematic therapy with local control treatments.The optimal timing of local control intervention,planning of sequential therapies,and implementation of multidisciplinary care remain pending.

Liver-specific therapies for metastases of neuroendocrine pancreatic tumors

The presence or development of liver metastases in patients with neuroendocrine pancreatic tumors is the most important prognostic factor.Liver resection,transplantation and many different therapeutic approaches are discussed in this special review.

Neuroendocrine tumors of the gastro-entero-pancreatic system

Gastro-entero-pancreatic (GEP) neuroendocrine tumors (NETs) are rare neoplasms, although their prevalence has increased substantially over the past three decades. Moreover, there has been an increased clinical recognition and characterization of these neoplasms. They show extremely variable biological behavior and clinical course. Most NETs have endocrine function and secrete peptides and neuroamines that cause distinct clinical syndromes, including carcinoid syndrome; however, many are clinically silent until late presentation with mass effects. Investigation and management should be individualized for each patient, taking into account the likely natural history of the tumor and general health of the patient. Management strategies include surgery for cure or palliation, and a variety of other cytoreductive techniques, and medical treatment including chemotherapy, and biotherapy to control symptoms due to hormone release and tumor growth, with somatostatin analogues (SSAs) and alphainterferon. New biological agents and somatostatintagged radionuclides are under investigation. Advances in the therapy and development of centers of excellence which coordinate multicenter studies, are needed to improve diagnosis, treatment and therefore survival of patients with GEP NETs.

Pancreatic neuroendocrine tumors: Therapeutic challenges and research limitations

Pancreatic neuroendocrine tumors(PNETs)are known to be the second most common epithelial malignancy of the pancreas.PNETs can be listed among the slowest growing as well as the fastest growing human cancers.The prevalence of PNETs is deceptively low;however,its incidence has significantly increased over the past decades.According to the American Cancer Society’s estimate,about 4032(>7%of all pancreatic malignancies)individuals will be diagnosed with PNETs in 2020.PNETs often cause severe morbidity due to excessive secretion of hormones(such as serotonin)and/or overall tumor mass.Patients can live for many years(except for those patients with poorly differentiated G3 neuroendocrine tumors);thus,the prevalence of the tumors that is the number of patients actually dealing with the disease at any given time is fairly high because the survival is much longer than pancreatic ductal adenocarcinoma.Due to significant heterogeneity,the management of PNETs is very complex and remains an unmet clinical challenge.In terms of research studies,modest improvements have been made over the past decades in the identification of potential oncogenic drivers in order to enhance the quality of life and increase survival for this growing population of patients.Unfortunately,the majority of systematic therapies approved for the management of advanced stage PNETs lack objective response or at most result in modest benefits in survival.In this review,we aim to discuss the broad challenges associated with the management and the study of PNETs.

Pancreatic neuroendocrine tumors: biology, diagnosis, and treatment

Pancreatic neuroendocrine tumors (PNETs), a group of endocrine tumors arising in the pancreas, are among the most common neuroendocrine tumors. The genetic causes of familial and sporadic PNETs are somewhat understood, but their molecular pathogenesis remains unknown. Most PNETs are indolent but have malignant potential. The biological behavior of an individual PNET is unpredictable; higher tumor grade, lymph node and liver metastasis, and larger tumor size generally indicate a less favorable prognosis. Endocrine testing, imaging, and histological evidence are necessary to accurately diagnose PNETs. A 4-pronged aggressive treatment approach consisting of surgery, locoregional therapy, systemic therapy, and complication control has become popular in academic centers around the world. The optimal application of the multiple systemic therapeutic modalities is under development; efficacy, safety, availability, and cost should be considered when treating a specific patient. The clinical presentation, diagnosis, and treatment of specific types of PNETs and familial PNET syndromes, including the novel Mahvash disease, are summarized.

Comparison of imaging-based and pathological dimensions in pancreatic neuroendocrine tumors

AIM To establish the ability of magnetic resonance(MR) and computer tomography(CT) to predict pathologic dimensions of pancreatic neuroendocrine tumors(Pan NET) in a caseload of a tertiary referral center.METHODS Patients submitted to surgery for Pan NET at the Surgical Unit of the Pancreas Institute with at least 1 preoperative imaging examination(MR or CT scan) from January 2005 to December 2015 were included and data retrospectively collected. Exclusion criteria were: multifocal lesions, genetic syndromes, microadenomas or mixed tumors, metastatic disease and neoadjuvant therapy. Bland-Altman(BA) and Mountain-Plot(MP) statistics were used to compare size measured by each modality with the pathology size. Passing-Bablok(PB) regression analysis was used to check the agreement between MR and CT.RESULTS Our study population consisted of 292 patients. Seventy-nine(27.1%) were functioning Pan NET. The mean biases were 0.17 ± 7.99 mm, 1 ± 8.51 mm and 0.23 ± 9 mm, 1.2 ± 9.8 mm for MR and CT, considering the overall population and the subgroup of non-functioning-Pan NET, respectively. Limits of agreement(LOA) included the vast majority of observations, indicating a good agreement between imaging and pathology. The MP further confirmed this finding and showed that the two methods are unbiased with respect to each other. Considering ≤ 2 cm non-functioning-Pan NET, no statistical significance was found in the size estimation rate of MR and CT(P = 0.433). PBR analysis did not reveal significant differences between MR, CT and pathology.CONCLUSION MR and CT scan are accurate and interchangeable imaging techniques in predicting pathologic dimensions of Pan NET.

Clinicopathological features of small nonfunctioning pancreatic neuroendocrine tumors

AIM:To present our experiences in studying the clinicopathological features of small nonfunctioning pancreatic neuroendocrine tumors(NF-p NETs).METHODS:The subjects included 9 patients with NFp NETs who underwent pancreatectomy between April1996 and September 2012.The surgical procedure,histopathological findings,and prognosis were assessed.RESULTS:All tumors were incidentally detected by computed tomography.The median diameter was 10mm(5-32 mm).One patient was diagnosed with von Hippel-Lindau disease,and the others were sporadiccases.For the histopathological findings,7 patients were G1;1 patient was G2;and 1 patient,whose tumor was 22 mm,had neuroendocrine carcinoma(NEC).One patient who had a tumor that was 32 mm had direct invasion to a regional lymph node and 1 patient with NEC,had regional lymph node metastases.Six of the 7 patients with sporadic NF-p NETs,excluding the patient with NEC,had tumors that were smaller than10 mm.Tumors smaller than 10 mm showed no malignancy and lacked lymph node metastasis.CONCLUSION:Sporadic NF-p NETs smaller than 10mm tend to have less malignant potential.These findings suggest that lymphadenectomy may be omitted for small NF-p NETs after further investigation.

Pancreatic neuroendocrine tumors G3 and pancreatic neuroendocrine carcinomas: Differences in basic biology and treatment

In 2017 the World Health Organization revised the criteria for classification of pancreatic neuroendocrine neoplasms(p NENs) after a consensus conference at the International Agency for Research on Cancer. The major change in the new classification was to subclassify the original G3 group into well-differentiated pancreatic neuroendocrine tumors G3(p NETs G3) and poorly differentiated pancreatic neuroendocrine carcinomas(p NECs), which have been gradually proven to be completely different in biological behavior and clinical manifestations in recent years. In 2019 this major change subsequently extended to NENs involving the entire digestive tract. The updated version of the p NENs grading system marks a growing awareness of these heterogeneous tumors. This review discusses the clinicopathological, genetic and therapeutic features of poorly differentiated p NECs and compare them to those of well-differentiated p NETs G3. For p NETs G3 and p NECs(due to their lower incidence), there are still many problems to be investigated. Previous studies under the new grading classification also need to be reinterpreted. This review summarizes the relevant literature from the perspective of the differences between p NETs G3 and p NECs in order to deepen understanding of these diseases and discuss future research directions.

Minimally invasive vs open pancreatectomy for nonfunctioning pancreatic neuroendocrine tumors

BACKGROUND The mainstay of treating nonfunctioning-pancreatic neuroendocrine tumors(NFPNETs)is surgical resection.However,minimally invasive approaches to pancreatic resection for treating NF-PNETs are not widely accepted,and the longterm oncological outcomes of such approaches remain unknown.AIM To determine the short-and long-term outcomes of minimally invasive pancreatic resection conducted in patients with NF-PNETs.METHODS Prospective databases from Severance Hospital were searched for 110 patients who underwent curative resection for NF-PNETs between January 2003 and August 2018.RESULTS The proportion of minimally invasive surgery(MIS)procedures performed for NF-PNET increased to more than 75%after 2013.There was no significant difference in post-operative complications(P=0.654),including pancreatic fistula(P=0.890)and delayed gastric emptying(P=0.652),between MIS and open approaches.No statistically significant difference was found in disease-free survival between the open approach group and the MIS group(median follow-up period,28.1 mo;P=0.428).In addition,the surgical approach(MIS vs open)was not found to be an independent prognostic factor in treating NF-PNET patients[Exp(β)=1.062;P=0.929].CONCLUSION Regardless of the type of surgery,a minimally invasive approach can be safe and feasible for select NF-PNET patients.

Functionality is not an independent prognostic factor for pancreatic neuroendocrine tumors

BACKGROUND Pancreatic neuroendocrine neoplasms(pNENs)that produce hormones leading to symptoms are classified as functional tumors,while others are classified as nonfunctional tumors.The traditional view is that functionality is a factor that affects the prognosis of pNEN patients.However,as the sample sizes of studies have increased,researches in recent years have proposed new viewpoints.AIM To assess whether functionality is an independent factor for predicting the prognosis of pNEN patients.METHODS From January 2004 to December 2016,data of patients who underwent surgery at the primary site for the treatment of pNENs from the Surveillance,Epidemiology,and End Results(SEER)database and West China Hospital database were retrospectively analyzed.RESULTS Contemporaneous data from the two databases were analyzed separately as two cohorts and then merged as the third cohort to create a large sample that was suitable for multivariate analysis.From the SEER database,age(P=0.006)and T stage(P<0.001)were independent risk factors affecting the survival.From the West China Hospital database,independent prognostic factors were age(P=0.034),sex(P=0.032),and grade(P=0.039).The result of the cohort consisting of the combined populations from the two databases showed that race(P=0.015),age(P=0.002),sex(P=0.032)and T stage(P<0.001)were independent prognostic factors.In the West China Hospital database and in the total population,nonfunctional pNETs and other functional pNETs tended to have poorer prognoses than insulinoma.However,functionality was not associated with the survival time of patients with pNETs in the multivariate analysis.CONCLUSION Functionality is not associated with prognosis.Race,age,sex,and T stage are independent factors for predicting the survival of patients with pNETs.

Active surveillance in metastatic pancreatic neuroendocrine tumors:A 20-year single-institutional experience

BACKGROUND Pancreatic neuroendocrine tumors(PanNETs)are heterogeneous and indolent;systemic therapy is not essential for every patient with metastatic PanNET.The National Comprehensive Cancer Network guidelines state that delaying treatment is an option for PanNET with distant metastasis,if the patient has stable disease.However,specific factors that influence surveillance were not mentioned.In addition,data regarding the period of active surveillance in patients with metastatic PanNET are lacking.AIM To specifically determine factors influencing active surveillance in patients with liver metastatic nonfunctioning PanNETs(NF-PanNETs).METHODS Seventy-six patients with liver metastatic NF-PanNETs who received active surveillance from a high-volume institution were enrolled.Time to disease progression(TTP)and time to initiation of systemic therapy were determined.RESULTS Thirty-one(40.8%)patients had recurrent liver disease after R0 resection;45(59.2%)were diagnosed with liver metastasis.The median follow-up period was 42 mo and 90.7%patients were observed to have disease progression.The median TTP(mTTP)was 10 mo.Multivariate analysis showed that the largest axis of the liver metastasis>5 mm(P=0.04),non-resection of the primary tumor(P=0.024),and T3-4 stage(P=0.028)were associated with a shorter TTP.The mTTP in patients with no risk factors was 24 mo,which was significantly longer than that in patients with one(10 mo)or more(6 mo)risk factors(P<0.001).A nomogram with three risk factors showed reasonable calibration,with a C-index of 0.603(95%confidence interval:0.47-0.74).CONCLUSION Active surveillance may only be safe for metastatic NF-PanNET patients with favorable risk factors,and other patients progressed rapidly without treatment.Further studies with a larger sample size and a control group are needed.

Pancreatic Neuroendocrine Tumors in the 21^stCentury—An Update

Pancreatic neuroendocrine tumors (PNETs) are rare, reported to account for less than 1% - 2% of all pancreatic tumors. This, however, is likely an underestimation, as improved radiologic techniques and heightened awareness have resulted in an increase in the detection of incidentalomas, with estimations of true prevalence as high as 10%. The term “PNET” is an umbrella name that encompasses a heterogeneous group of neoplasms each with distinct clinical presentations, diagnostic radiographic features, management principles, and tumor/patient outcomes. In this context, accurate diagnosis is challenging, and management guidelines remain unclear. A high degree of clinical suspicion is required for best patient management. This manuscript provides an update on PNETs in the 21st century, in which we re-examine the terminology, epidemiology, classification, etiopathogenesis, radiographic and histopathologic diagnostic features, management for localized and metastatic disease, as well as a review of features defining functional and non-functional PNETS, and finally deliberates on the prognosis and predictive features of this unpredictable and largely unfathomable neoplasm.