Unmet Needs in Appendiceal Neuroendocrine Neoplasms

Retrospective analysis of criteria for oncological completion surgery of neuroendocrine tumors of the appendix

PURPOSE

Neuroendocrine neoplasms of the appendix (aNET) are rare tumors that are often diagnosed by pathology as an incidental finding after appendectomy for acute appendicitis. Several guidelines proposed risk criteria to indicate oncological completion surgery after appendectomy. The aim of this study was to evaluate the reliability of proposed criteria for completion surgery of aNET.

METHODS

Patients with aNET treated at ENETS center of excellence Marburg between 2002 and 2022 were retrieved from a prospective data base. Demographic data, histopathological findings, including formerly proposed criteria to indicate oncological completion surgery, histological results of the completion resection and disease-free survival were evaluated.

RESULTS

82 patients with a median age of 35 (range 8-82) years were analysed. 72 (88%) patients underwent an emergency appendectomy because of acute appendicitis. 11 (13%) patients received an ileocecal resection or right hemicolectomy. Seven (8.5%) patients had lymph node metastases and three (3.6%) patients had distant metastases at the initial operation. 27 (33%) patients underwent completion surgery by right hemicolectomy according to guideline criteria, but postoperative histology detected lymph node and distant metastases in only six (22%) and zero patients resulting in an overtreatment of 21 (75%) patients. A tumor size of > 2 cm was the only significant criterion which was associated with lymph node metastases (p < 0.05). After a median follow-up of 62 months (range 2-264) 76 (96%) of the patients in stages I to III were alive with no evidence of disease.

CONCLUSION

aNET have an excellent prognosis in stages I-III and distant metastases are rare. Formerly proposed criteria for oncological completion surgery have to be adopted and discussed for every patient, as they might result in an overtreatment in at least 75% of patients.

Appendiceal Neuroendocrine Neoplasms: A Comprehensive Review

ABSTRACT

Appendiceal neuroendocrine neoplasm (NEN) is the most common adult appendiceal malignant tumor, constituting 16% of gastrointestinal NENs. They are versatile tumors with varying morphology, immunohistochemistry, secretory properties, and cancer genomics. They are slow growing and clinically silent, to begin with, or present with features of nonspecific vague abdominal pain. Most acute presentations are attributed clinically to appendicitis, with most cases detected incidentally on pathology after an appendectomy. Approximately 40% of them present clinically with features of hormonal excess, which is likened to the functional secretory nature of their parent cell of origin. The symptoms of carcinoid syndrome render their presence clinically evident. However, slow growing and symptomatically silent in its initial stages, high-grade neuroendocrine tumors and neuroendocrine carcinomas of the appendix are aggressive and usually have hepatic and lymph node metastasis at presentation. This review article focuses on imaging characteristics, World Health Organization histopathological classification and grading, American Joint Committee on Cancer/Union or International Cancer Control, European Neuroendocrine Tumor Society staging, European Neuroendocrine Tumor Society standardized guidelines for reporting, data interpretation, early-stage management protocols, and advanced-stage appendiceal NENs. Guidelines are also set for the follow-up and reassessment. The role of targeted radiotherapy, chemotherapy, and high-dose somatostatin analogs in treating advanced disease are discussed, along with types of ablative therapies and liver transplantation for tumor recurrence. The search for newer location-specific biomarkers in NEN is also summarized. Regarding the varying aggressiveness of the tumor, there is a scope for research in the field, with plenty of data yet to be discovered.

[Current developments in the treatment of neuroendocrine tumors]

BACKGROUND

Well-differentiated neuroendocrine tumors (NET) are rare malignancies that are clinically very heterogeneous. Accordingly, their treatment is also complex and dependent on various factors. With currently available systemic therapies, the prognosis is often favorable.

OBJECTIVES

This article aims to provide an overview of current treatment strategies for NET, addressing the most important NET locations.

METHODS

The current European guidelines and further relevant literature on the treatment of NET were reviewed for this purpose.

RESULTS

The therapeutic spectrum for NET is extremely broad: For NET of the stomach/duodenum, appendix, and rectum, endoscopic or surgical resection is often sufficient, and metastatic tumors are rare. NET of the pancreas, small intestine and lung should also undergo potentially curative resection in the early stages. In the metastatic stage, locoregional treatments such as surgery and liver tumor embolization play a role. Major advances have been made in drug therapy, with somatostatin analogs (octreotide and lanreotide), an mTOR inhibitor (everolimus), and a tyrosine kinase inhibitor (sunitinib) being widely used. Peptide receptor radionuclide therapy (PRRT) is also an invaluable option. In some cases, classic chemotherapy is indicated.

CONCLUSIONS

Many effective therapies are now available for NET. It is important to select the right therapy at the right time for each patient through interdisciplinary management.

ASO Practice Guidelines Series: Surgical Management of Gastrointestinal (Midgut) Neuroendocrine Neoplasms

Gastrointestinal midgut neuroendocrine neoplasms (NENs) are a heterogeneous group of uncommon malignancies. For well-differentiated NENs, known as neuroendocrine tumors (NETs), surgery is a cornerstone of management in localized and metastatic disease. Because of heterogeneous tumor behaviour, association with endocrine syndrome, and prognosis, the management of NETs must be individualized to all these factors in addition to the primary site. With the fast pace of advancement in the field, both for therapies and understanding of tumoral etiology and behaviour, it is important for surgical oncologists to remain updated on guidelines recommendations and suggested treatment pathways. Those guidelines provide important guidance for management of NETs but are largely based on expert opinions and interpretation of retrospective evidence. This article reviews highlights of most recent practice guidelines for midgut (gastric, duodenal, small intestinal, and appendiceal) NETs.

Appendiceal Neuroendocrine Neoplasms: an Update for 2023

PURPOSE OF REVIEW

To summarize the literature from the last 5 years on treatment of appendiceal neuroendocrine neoplasms (aNEN). Furthermore, to evaluate the prognostic significance of lymph node metastases, indications for adjuvant treatment, and challenges of the current follow-up regimen.

RECENT FINDINGS

Simple appendectomy is sufficient in tumors < 1 cm while extended surgery is indicated in tumors > 2 cm. In a multicenter study of aNENs measuring 1-2 cm, extended surgery offered no significant prognostic advantage and is now limited to incomplete tumor resection or high-grade G2 or G3 aNEN. Follow-up remains debatable, as the use of imaging and biomarkers lacks validation. While surgical procedure is well established in aNEN tumors < 1 cm and > 2 cm, the need for extended surgery in aNEN tumors 1-2 cm is questionable. Future studies should address the prognostic impact of lymph node metastases and the optimal design and duration of follow-up.

Incidence and Management of Appendiceal Neuroendocrine Tumors in Pediatric Population: A Bicentric Experience with 6285 Appendectomies

BACKGROUND

Neuroendocrine tumors (NETs) are rare tumors that arise from neuroendocrine cells and are the most common tumors of the appendix. NETs of the appendix usually cause no symptoms and often go unnoticed until they cause acute appendicitis or are discovered during an accidental appendectomy. As the trend towards the conservative treatment of acute appendicitis increases in the pediatric population, the question arises as to whether the majority of NETs go undetected and are only discovered at an advanced stage. The purpose of the proposed study is to review the incidence and outcomes of treatment for NETs of the appendix in children and include the data presented in the data pool for further review.

METHODS

From 1 January 2009 to 1 November 2023, a total of 6285 appendectomies were performed in two large pediatric centers in Croatia. After a retrospective review of the case records and histopathologic findings, a total of 31 children (0.49%) were diagnosed with NET of the appendix and included in the further analysis. The primary outcome of this study was the incidence and treatment outcome of pediatric patients diagnosed with NET of the appendix. Secondary outcomes included the patients' demographic, clinical, and laboratory data and the histopathologic characteristics of tumor species.

RESULTS

The overall incidence of NETs of the appendix was stable over the study years, with minor fluctuations. The median age of patients was 14 (interquartile range-IQR: 12, 16) years, with a female predominance (64.5%). The majority of patients (96.8%) presented with acute abdominal pain and underwent appendectomy because acute appendicitis was suspected. Acute appendicitis was confirmed by histopathology in 18 (58%) cases. NETs of the appendix were not detected preoperatively in any of the patients. Among patients with confirmed acute appendicitis, most (n = 14; 77.8%) were found to have non-perforated acute appendicitis. In most children, the tumor was located at the tip of the appendix (n = 18; 58.1%), and the majority of tumors had a diameter of less than 1 cm (n = 21, 67.7%). The mitotic count (n = 25, 80.6%) and Ki-67 proliferation index (n = 23, 74.2%) were low in most patients, so most tumors were classified as NET G1 (n = 25, 80.6%), while NET G2 and NET G3 were found in four (12.9%) and two (6.5%) patients, respectively. All children were treated with appendectomy only. The median follow-up time was 54 (IQR: 24, 95) months.

CONCLUSIONS

The incidence of appendiceal NET among pediatric patients is very low. NET occurs most frequently in adolescents, with a female predominance. Most tumors are less than 1 cm in diameter, located at the tip, and associated with non-perforated appendicitis. Appendectomy is the treatment of choice, and major surgery was not necessary in our cohort.

The Driver Role of Pathologists in Endocrine Oncology: What Clinicians Seek in Pathology Reports

Endocrine neoplasia represents an increasingly broad spectrum of disorders. Endocrine neoplasms range from incidental findings to potentially lethal malignancies. In this paper, we cover the impact of pathology in the interpretation of the clinic-pathological, genetic, and radiographic features underpinning these neoplasms. We highlight the critical role of multidisciplinary interactions in structuring a rational diagnostic and efficient therapeutic plan and emphasize the role of histopathological input in decision-making. In this context, standardized pathology reporting and second opinion endocrine pathology review represent relevant tools to improve the overall diagnostic workup of patients affected by endocrine tumors in every specific scenario. In fact, although a relevant proportion of cases may be correctly identified based on clinical presentation and biochemical/imaging investigations, a subset of cases presents with atypical findings that may lead to an inappropriate diagnosis and treatment plan based on a wrong pathological diagnosis if all pieces of the puzzle are not correctly considered. Pathologists have a responsibility to actively guide clinicians before and during surgical procedures to prevent unnecessary interventions. In all areas of endocrine pathology, pathologists must understand the complexity of tissue preservation and assay sensitivities and specificities to ensure the optimal quality and interpretation of diagnostic material. Finally, pathologists are central actors in tumor tissue biobanking, which is an expanding field in oncology that should be promoted while adhering to strict ethical and methodological standards.

Site-specific trends in gastroenteropancreatic neuroendocrine neoplasms in Bavaria, Germany

INTRODUCTION

Neuroendocrine neoplasms (NEN) are rare and heterogeneous epithelial tumors, occurring throughout the body. For gastroenteropancreatic (GEP)-NEN, rising incidence rates were reported for the last decades, with underlying causes remaining largely unexplained. We evaluated NEN trends stratifying by their histologic subtypes.

METHODS

Incident cases of GEP-NEN diagnosed between 2005 and 2019 were retrieved from the prospective, population-based Bavarian Cancer Registry. GEP-NEN were divided in their histologic subtypes, that is, neuroendocrine tumors (NET) G1, NET G2/G3, other NET versus small-cell neuroendocrine carcinoma (NEC), large-cell NEC, and other NEC. We calculated annual age-standardized incidence rates (ASIRs) per 100,000 persons for the total of GEP-NEN, NEN histologic subtypes, and tumor sites. We used an annual percentage change (APC) approach including a joinpoint analysis to investigate NEN incidence trends.

RESULTS

ASIR of GEP-NEN rose from 2.2 in 2005 to 4.8 in 2019, characterized by a significant increase until 2012 (APC 2005-2012: 10.1%), followed by modest rise (APC 2012-2019: 1.5%). In the last decade, this increase was mainly driven by the rise of NET G1 and G2/G3, while incidence for NEC declined. Over the study period, ASIR increased significantly for all GEP-sites except the colon. APCs were largest for the stomach, the appendix, the pancreas, and the rectum.

CONCLUSIONS

This study found a significant increase in the incidence of GEP-NET. Though this development may partially be attributable to the increased use of advanced detection techniques and changes in NEN classification, further research should also focus on the identification of NEN risk factors.

European Neuroendocrine Tumor Society (ENETS) 2023 guidance paper for appendiceal neuroendocrine tumours (aNET)

The aim of the present guidance paper is to update the previous ENETS guidelines on well differentiated appendiceal neuroendocrine tumours (NET), providing practical guidance for the diagnosis and management of appendiceal NET (aNET); poorly differentiated neoplasms are dealt with in a separate guidance paper. This paper is structured on a question-answer format in order to also address controversial issues and areas where uncertainty regarding the management and follow-up of aNET exists. All recommendations are offered on the basis of the best available evidence, along with the authors' experiences in managing these neoplasms. Each recommendation for treatment will provide a level of evidence and grade of recommendation as per the GRADE system (adapted in Infectious Disease Society of United States Public Health Service grading system).

Clinical features and outcomes of appendiceal neuroendocrine tumours: 10 year audit from the Irish NET Centre of Excellence

Appendiceal neuroendocrine tumours (aNETs) are rare neoplasms of the gastrointestinal tract often diagnosed incidentally at the time of appendicectomy. Appendicectomy is considered curative in the majority of cases but guidelines recommend right-sided hemicolectomy (RHC) for those with specific high-risk features despite no data supporting a survival benefit. We performed a retrospective search of multi-disciplinary tumour board and pathology databases from 2012 to 2022 to identify cases of aNET treated at our centre. Follow-up data were obtained from the electronic healthcare records. A total of 142 cases of aNET were included for analysis. Mean age at presentation was 34, of which 76% were female and 92% of aNETs were located in the tip/middle of the appendix; 90% were grade 1, and 93% had R0 resection. Tumour size was <1 cm in 54%, 1-2 cm in 36%, >2 cm in 9%. A total of 43 patients (30%) underwent RHC with lymph node metastases identified in 16 (37%). Lymph node metastases were associated with tumour size >2 cm (p = .008) and higher tumour grade (p = .041) on multivariate analysis. For aNET 1-2 cm, lymph node metastases were identified in 7/22 who had RHC (32%) with tumour grade the only significant risk factor (p = .046). Distant metastases were identified in 2 cases (1%), diagnosed synchronously and associated with grade 2 tumours. Overall survival for those with lymph node metastases was 100% after a median 4 years. Progression-free survival was 93%, with a single case of disease progression associated with synchronous distant metastases at initial diagnosis. Lymph node metastases in aNET are associated with higher tumour grade and tumour size >2 cm. Disease progression in the setting of lymph node metastases is rare. The significance of lymph node metastases and need for completion RHC remains uncertain.

Optimal surgical approach for digestive neuroendocrine neoplasia primaries: Oncological benefits versus short and long-term complications

The rising incidence and the accumulating prevalence of neuroendocrine neoplasia (NEN) in the population makes this a common, prevalent and a clinically relevant disease group. Surgical resection represents the only potentially curative treatment for digestive NENs. Thus, resection should in principle be considered for all patients with NEN, although taking the patients age, relevant comorbidity, and performance status into account for operability. Patients with insulinomas, NEN of the appendix and rectal NENs are usually cured by surgery alone. However, less than a third of patients are amendable to curative surgery alone at time of diagnosis. Furthermore, recurrence is common and may occur years after primary surgery, hence the long follow-up time recommended in most NENs (>10 years). As many patients with NENs present with locoregional or metastatic disease, there is considerable debate regarding the role of debulking surgery in these settings. However, good long-term survival can be achieved in a considerable proportion of patients, with 50-70% alive up to 10 years after surgery. Location and grade are the main determinants of long-term survival. Here we present considerations to surgery for primary neuroendocrine tumors in the digestive tract.

Prognostic impact of number of examined lymph nodes on survival of patients with appendiceal neuroendocrine tumors

BACKGROUND

The prognosis of patients with appendiceal neuroendocrine tumors (ANETs) is related to lymph node (LN) metastasis and other factors. However, it is unclear how the number of examined LNs (ELNs) impact on survival.

AIM

To determine the factors affecting the cancer-specific survival (CSS) of patients with ANET and to evaluate the impact of the number of ELNs on survival.

METHODS

A total of 4583 ANET patients were analyzed in the Surveillance, Epidemiology, and End Results database. Univariate survival analysis was used to identify factors related to survival and the optimal number of ELNs and lymph node ratio (LNR) were determined by the Kaplan–Meier method. The survival difference was determined by CSS.

RESULTS

Except for sex, the other factors, such as age, year, race, grade, histological type, stage, tumor size, ELNs, LNR, and surgery type, were associated with prognosis. The 3-, 5-, and 10-year CSS rates of ANET patients were 91.2%, 87.5, and 81.7%, respectively (median follow-up period of 31 mo and range of 0-499 mo). There was no survival difference between the two surgery types, namely, local resection and colectomy or greater, in both stratifications of tumor size ≥ 2 cm (P = 0.523) and < 2 cm (P = 0.068). In contrast to patients with a tumor size < 2 cm, those with a tumor size ≥ 2 cm were more likely to have LN metastasis (χ² = 378.16, P < 0.001). The optimal number of ELNs was more than 11, 7, and 18 for all patients, node-negative patients, and node-positive patients, respectively. CSS rates of patients with a larger number of ELNs were significantly improved (≤ 10 vs ≥ 11, χ² = 20.303, P < 0.001; ≤ 6 vs ≥ 7, χ² = 11.569, P < 0.001; ≤ 17 vs ≥ 18, χ² = 21.990, P < 0.001; respectively). ANET patients with an LNR value ≤ 0.16 were more likely to have better survival than those with values of 0.17-0.48 (χ² = 48.243, P < 0.001) and 0.49-1 (χ² = 168.485, P < 0.001).

CONCLUSION

ANET ≥ 2 cm are more likely to develop LN metastasis. At least 11 ELNs are required to better evaluate the prognosis. For patients with positive LN metastasis, 18 or more LNs need to be detected and lower LNR values (LNR ≤ 0.16) indicate a better survival prognosis.

Diagnosis, treatment, and current concepts in the endoscopic management of gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are rare tumors derived from the neuroendocrine cell system, which that have increased in incidence and prevalence in recent years. Despite improvements in radiological and metabolic imaging, endoscopy still plays a pivotal role in the number of GEP-NENs. Tumor detection, characterization, and staging are essential in management and treatment planning. Upper and lower gastrointestinal (GI) endoscopy is essential for correct localization of the primary tumor site of GI NENs. Endoscopic ultrasonography (EUS) has an important role in the imaging and tissue acquisition of pancreatic NENs and locoregional staging of GI neuroendocrine tumors. Correct staging and histological diagnosis have important prognostic implications. Endoscopic operating techniques allow the removal of small GI NENs in the early stage of mucosal or submucosal invasion of the intestinal wall. Preoperative EUS-guided techniques may help the surgeon locate small and deep tumors, thus avoiding formal pancreatic resections in favor of parenchymal-sparing surgery. Finally, locoregional ablative treatments have been proposed in recent studies with promising results in selected patients.

Appendiceal Neuroendocrine Tumor Detected by 18F-FDG PET/CT

ABSTRACT

Appendiceal neuroendocrine tumor is very rare, and it is difficult to make a definite diagnosis before operation due to absence of specific clinical features. We report the 18F-FDG PET/CT findings in a patient with an appendiceal neuroendocrine tumor.

Time to give up traditional methods for the management of gastrointestinal neuroendocrine tumours

Neuroendocrine tumors (NETs) are a rare and heterogeneous disease group and constitute 0.5% of all malignancies. The annual incidence of NETs is increasing worldwide. The reason for the increase in the incidence of NETs is the detection of benign lesions, incidental detection due to the highest use of endoscopic and imaging procedures, and higher recognition rates of pathologists. There have been exciting developments regarding NET biology in recent years. Among these, first of all, somatostatin receptors and downstream pathways in neuroendocrine cells have been found to be important regulatory mechanisms for protein synthesis, hormone secretion, and proliferation. Subsequently, activation of the mammalian target of rapamycin pathway was found to be an important mechanism in angiogenesis and tumor survival and cell metabolism. Finally, the importance of proangiogenic factors (platelet-derived growth factor, vascular endothelial growth factor, fibroblastic growth factor, angiopoietin, and semaphorins) in the progression of NET has been determined. Using the combination of biomarkers and imaging methods allows early evaluation of the appropriateness of treatment and response to treatment.

Lessons learned about appendiceal neuroendocrine neoplasms from data analysis of the Belgian Cancer Registry 2010-2015

BACKGROUND AND STUDY AIMS

Appendiceal neuroendocrine neo-plasms (aNENs) are a diverse group of malignant neoplasms of varying biological behavior for which information about manage-ment and outcome is sparse, with the majority of available studies being retrospective, including only a limited number of patients, and therefore not necessarily reflecting the reality in the community. In the present study clinical, epidemiological and pathological data of appendiceal neuroendocrine neoplasms in Belgium is provided and compared with current literature.

METHODS

A population-based study was conducted by linking data of the Belgian Cancer Registry with medical procedures in the Belgian Health Insurance database for patients diagnosed with aNEN between 2010 and 2015.

RESULTS

We found an aNEN incidence of 0.97/100.000 person years in Belgium. Neuroendocrine carcinoma of the appendix are rare. Most appendiceal neuroendocrine tumors (aNETs) are small G1 tumors. Positive lymph nodes are often found in tumors larger than 2cm, especially aNET G2.

CONCLUSION

A rapid uptake of changing classifications was seen in the community. However, systematic reporting of risk factors for small aNEN can still be improved and should be stimulated. In 9% of cases, reclassifications had to be made, pointing out that in a retrospective analysis, original pathological reports should be checked for specific parameters, before reliable conclusions can be drawn.

A Predictive Model for Nodal Metastases in Patients With Appendiceal Cancers

BACKGROUND

Histologic subtypes of appendiceal cancer vary in their propensity for metastases to regional lymph nodes (LN). A predictive model would help direct subsequent surgical therapy.

METHODS

The National Cancer Database was queried for patients with appendiceal cancer undergoing surgery between 1998 and 2012. Multivariable logistic regression was used to develop a predictive model of LN metastases which was internally validated using Brier score and Area under the Curve (AUC).

RESULTS

A total of 21,647 patients were identified, of whom 9079 (41.9%) had node negative disease, 4575 (21.1%) node positive disease, and 7993 (36.9%) unknown LN status. The strongest predictors of LN positivity were histology (carcinoid tumors OR 12.78, 95% CI 9.01-18.12), increasing T Stage (T3 OR 3.36, 95% CI 2.52-4.50, T4 OR 6.30, 95% CI 4.71-8.42), and tumor grade (G3 OR 5.55, 95% CI 4.78-6.45, G4 OR 5.98, 95% CI 4.30-8.31). The coefficients from the regression analysis were used to construct a calculator that generated predicted probabilities of LN metastases given certain inputs. Internal validation of the overall model showed an AUC of 0.75 (95% CI 0.74-0.76) and Brier score of 0.188. Histology-specific predictive models were also constructed with an AUC that varied from 0.669 for signet cell to 0.75 for goblet cell tumors.

CONCLUSIONS

The risk for nodal metastases in patients with appendiceal cancers can be quantified with reasonable accuracy using a predictive model incorporating patient age, sex, tumor histology, T-stage, and grade. This can help inform clinical decision making regarding the need for a right hemicolectomy following appendectomy.

Risk factors for progression of appendiceal neuroendocrine tumours: low-stage tumours <5 mm appear to be overwhelmingly indolent and may merit a separate designation

AIMS

Appendiceal well-differentiated neuroendocrine tumours (NETs) are usually incidental and clinically benign. Several studies have reported different risk factors for nodal metastasis. The aim of this study was to investigate our appendiceal NETs (App-NETs) to determine the factors associated with malignant behaviour.

METHODS AND RESULTS

For 120 App-NETs, we reviewed the clinical presentation and follow-up, including serum chromogranin A (CgA) levels, and compiled several microscopic variables. Pathological factors were compared with nodal status and time to biochemical recurrence (elevated serum CgA level) by the use of Cox regression. We also reviewed similar App-NET data in the Surveillance, Epidemiology, and End Results (SEER) Programme. Among our 120 cases, seven patients had positive lymph nodes, and nine developed subsequent elevation of CgA levels; none developed distant metastases or died of disease. Only three patients had grade 2 NETs; none had nodal disease, and one developed an elevated CgA level. Increasing tumour size was associated with an increased risk of nodal disease [odds ratio (OR) 4.99, P = 0.0055). All seven node-positive cases were ≥13 mm. Factors associated with elevated CgA levels included age (OR 1.04, P = 0.041), pT4 disease (OR 10.22, P = 0.033), and nodal disease (OR 24.0, P = 0.012), but not size (OR 2.13, P = 0.072). Of the 1492 reported App-NETs in the SEER database with data on tumour size, 137 (9%) were pN1; only five of these (4%) were coded as being <5 mm.

CONCLUSIONS

Small (<5 mm) App-NETs that do not invade the serosa or mesoappendix appear to be overwhelmingly benign and low-grade, requiring neither Ki67 staining nor synoptic reporting. Given their indolent behaviour, different nomenclature or staging may be more appropriate for these NETs.

Temporal trends in incidence, evaluation and management of neuroendocrine neoplasms of the appendix: 14 years' experience

BACKGROUND

Information regarding temporal trends in appendiceal neuroendocrine neoplasms (ANEN) is limited. This retrospective study evaluated temporal trends in ANEN incidence and management over a 14-year period.

METHODS

Appendectomy pathology reports from a single tertiary center were reviewed.

RESULTS

During 2005-2018, 8327 appendectomies were performed and 57 ANENs were diagnosed (average age 31.7 ± 17 years; 70.2% women; 17.5% Arab ethnicity; and 22.8% < 18 years of age). The cohort was divided according to year of diagnosis (Period A 2005-2011; Period B 2012-2018). No differences were found in ANEN incidence (0.75% and 0.62%, respectively, p = 0.104), epidemiologic or pathologic characteristics between periods. In period B, pathology reports were more comprehensive and use of specific imaging and biochemical studies was more prevalent. Hemicolectomy rates and results were similar (8 in Period A, 7 in Period B, p = 0.925). All patients remained alive for the duration of follow-up.

CONCLUSIONS

No temporal changes in epidemiological, clinical or pathological features of ANENs were noted. Although clinico-pathological evaluation was more detailed after 2011, there was no change in rates of hemicolectomy or disease prognosis.

Lights and darks of neuroendocrine tumors of the appendix

INTRODUCTION

Neuroendocrine tumors of the appendix are a relatively frequent type of neuroendocrine tumor, usually detected incidentally after appendectomy. Almost all small slow-growing G1 tumors with no risk factors are cured with appendectomy while the rare and aggressive G3 carcinomas may represent a challenge in terms of management and often lead to a poor outcome. In the middle of the spectrum, a number of tumors present with in-between features and sometimes no clear-cut guidance emerges from the literature for directing the management and follow-up of these patients.

EVIDENCE ACQUISITION

A meticulous review of the literature on neuroendocrine tumors of the appendix, including the recommendations published by the relevant international societies.

EVIDENCE SYNTHESIS

The literature on the neuroendocrine tumors of the appendix appears to be inhomogeneous. Likely this occurs as a consequence of a number of factors, including the mostly retrospective nature of the available data, the heterogeneous records of the same, and some peculiar aspects of the appendiceal neuroendocrine tumors, with evidence of considerable biological and clinical differences in terms of epidemiology, management, and prognosis from the less aggressive tumors to the most aggressive cancers. In particular, some situations concerning tumors in the middle of the biological and clinical spectrum are still poorly defined.

CONCLUSIONS

There are some persisting "grey areas" with regard to the characterization and the clinical management of neuroendocrine tumors of the appendix. An increasing awareness of the biological and clinical aspects of this disease and new, ideally prospective, focused studies might help and clarify some relevant issues that are not fully elucidated yet and could increase the solidity of the guidance for the management and the follow-up of the patients.

Neuroendocrine Tumors of the Gastrointestinal Tract and Pancreas

Neuroendocrine neoplasms (NENs) of the gastrointestinal (GI) tract and pancreas are a rare and heterogeneous group of neoplasms characterized by common cellular features as well as unique site-specific traits. GI and pancreatic NENs are much rarer than the more common adenocarcinomas arising at these sites. However, the incidences of GI and pancreatic NENs have increased significantly, particularly in the stomach and common site, followed by rectum, appendix, colon, and stomach. Pancreatic NENs are also uncommon, with fewer than 1 per 100,000, accounting for 1% to 2% of all pancreatic neoplasms.

The risk of lymph node metastases and their impact on survival in patients with appendiceal neuroendocrine neoplasms: a systematic review and meta-analysis of adult and paediatric patients

BACKGROUND

There are no clear histopathological parameters determining the risk of lymph node (LN) metastases and appropriateness of completion prophylactic right hemicolectomy (RHC) in patients with appendiceal neuroendocrine neoplasms (ANENs).

MATERIALS AND METHODS

The PubMed, Cochrane Library, Embase, Web of Science and SCOPUS databases were searched up to November 2018. Quality/risk of bias was assessed using the Newcastle-Ottawa Scale (NOS).

RESULTS

A total of 526 articles were screened. In 11 adult and 3 paediatric studies, 602 and 77 unique patients, respectively, with ANEN and undergoing RHC, were included. The rate of LN metastases for a cutoff size >10 mm was 48.6% (vs 12.1% for lesions <10 mm) among adult patients, with an odds ratio (OR) of 4.8 (95% CI, 1.5-15.8). For 20 mm size cutoff, these figures were 61% (vs 28.2% for lesions <20 mm) with an OR of 3.2 (95% CI, 1.3-7.8). Vascular-, lymph vessel- and perineural invasions were identified as predictive factors for LN metastases in adult patients. In paediatric patients, there were no strong morphological predictors for LN metastases. The 10-year disease-specific survival (DSS) for adult patients without LN metastases was 99.2% vs 95.6% in patients with LN (OR: 0.2; 95% CI, 0.02-2.4). The complication rate of prophylactic RHC was 11.4%.

CONCLUSIONS

This meta-analysis demonstrates that tumour size >20 mm as well as >10 mm and/or vascular-, lymph vessel- and perineural invasions are associated with increased risk for LN metastases in adult patients with ANEN. The prognostic value of LN positivity remains to be determined in further studies with long-term follow-up.

Appendiceal neuroendrocrine neoplasms: incidentaloma or something we should worry about?

PURPOSE OF REVIEW

To synthesize the current knowledge and guidelines on the management of appendiceal neuroendocrine neoplasms (ANENs).

RECENT FINDINGS

Most recent guidelines are essentially based on heterogeneous retrospective series. With the advent of a more precise classification of neuroendocrine neoplasms, this heterogeneity is rightly criticized and many 'grey areas' are now debated in expert literature. The only way to solve these issues is through the conduct of large prospective multicentre studies, but this seems somewhat utopian, given the rarity of this disease.

SUMMARY

ANENs are rare tumours with a favourable prognosis, and mainly diagnosed in young patients. They are predominantly localized, and diagnosed incidentally on appendectomy. This procedure is curative for the vast majority of patients but ANENs can relapse even a significant time after the first diagnosis. Identifying the risks for recurrence is challenging, with some factors thought to be predictive of nodal involvement. The presence of one or more of these factors justifies an oncological radicalization of the surgical procedure (right hemicolectomy with lymphadenectomy). However, the beneficial impact of this surgical procedure on survival is still unproven.