Neuroendocrine neoplasms of the appendix: Characterization of 335 patients referred to the Copenhagen NET Center of Excellence

The Clinicopathological Significance of Tumor Cell Subtyping in Appendiceal Neuroendocrine Tumors: A Series of 135 Tumors

Appendiceal neuroendocrine tumors (NETs) are common and often are identified as incidental lesions at the time of appendectomy. The guidelines for management are based on tumor size, degree of invasion, and the Ki67 proliferation index. Most small bowel NETs are composed of serotonin-producing EC-cells, but there are multiple other neuroendocrine cell types. In the rectum, there are L-cell tumors that express peptide YY (PYY), glucagon-like peptides (GLPs), and pancreatic polypeptide (PP); they are thought to have a better prognosis than serotonin-producing tumors. We investigated whether the appendix has distinct neuroendocrine tumor types based on cell type and whether that distinction has clinical significance. We collected 135 appendiceal NETs from the pathology archives of UHN Toronto and UHCMC (Cleveland). We analyzed the expression of biomarkers including CDX2, SATB2, PSAP, serotonin, glucagon (that detects GLPs), PYY, and pancreatic polypeptide (PP) and correlated the results with clinicopathologic parameters. Immunohistochemistry identified three types of appendiceal NETs. There were 75 (56%) classified as EC-cell tumors and 37 (27%) classified as L-cell tumors; the remaining 23 (17%) expressed serotonin and one of the L-cell biomarkers and were classified as mixed. EC-cell tumors were significantly larger with more extensive invasion involving the muscularis propria, subserosa, and mesoappendix compared with L-cell tumors. Mixed tumors were intermediate in all of these parameters. Both EC-cell and mixed tumors had lymphatic and/or vascular invasion while L-cell tumors had none. Unlike EC-cell NETs, L-cell tumors were not associated with lymph node metastasis. Tumor type correlated with pT stage and the only patient with distant metastatic disease in this series had an EC-cell tumor. Our study confirms that appendiceal NETs are not a homogeneous tumor population. There are at least three types of appendiceal NET, including EC-cell, L-cell, and mixed tumors. This information is important for surveillance of patients, as monitoring urinary 5HIAA levels is only appropriate for patients with serotonin-producing tumors, whereas measurement of GLPs and/or PP is more appropriate for patients with L-cell tumors. Our data also show that tumor type is of significance with EC-cell tumors exhibiting the most aggressive behavior.

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.

Comparative prognosis and risk assessment in gallbladder neuroendocrine neoplasms versus adenocarcinomas

Background

Gallbladder neuroendocrine neoplasms (GB-NENs) are a rare malignant disease, with most cases diagnosed at advanced stages, often resulting in poor prognosis. However, studies regarding the prognosis of this condition and its comparison with gallbladder adenocarcinomas (GB-ADCs) have yet to yield convincing conclusions.

Methods

We extracted cases of GB-NENs and GB-ADCs from the Surveillance, Epidemiology, and End Results (SEER) database in the United States. Firstly, we corrected differences in clinical characteristics between the two groups using propensity score matching (PSM). Subsequently, we visualized and compared the survival outcomes of the two groups using the Kaplan-Meier method. Next, we employed the least absolute shrinkage and selection operator (LASSO) regression and Cox regression to identify prognostic factors for GB-NENs and constructed two nomograms for predicting prognosis. These nomograms were validated with an internal validation dataset from the SEER database and an external validation dataset from a hospital. Finally, we categorized patients into high-risk and low-risk groups based on their overall survival (OS) scores.

Results

A total of 7,105 patients were enrolled in the study, comprising 287 GB-NENs patients and, 6,818 GB-ADCs patients. There were substantial differences in clinical characteristics between patients, and GB-NENs exhibited a significantly better prognosis. Even after balancing these differences using PSM, the superior prognosis of GB-NENs remained evident. Independent prognostic factors selected through LASSO and Cox regression were age, histology type, first primary malignancy, tumor size, and surgery. Two nomograms for prognosis were developed based on these factors, and their performance was verified from three perspectives: discrimination, calibration, and clinical applicability using training, internal validation, and external validation datasets, all of which exhibited excellent validation results. Using a cutoff value of 166.5 for the OS nomogram score, patient mortality risk can be identified effectively.

Conclusion

Patients with GB-NENs have a better overall prognosis compared to those with GB-ADCs. Nomograms for GB-NENs prognosis have been effectively established and validated, making them a valuable tool for assessing the risk of mortality in clinical practice.

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.

Surgical management of 1- to 2-cm neuroendocrine tumors of the appendix: Appendectomy or right hemicolectomy?

BACKGROUND

The surgical management of 1- to 2-cm neuroendocrine tumors of the appendix is an area of debate. We analyzed the clinical outcomes of appendectomy and compared them to right hemicolectomy.

METHODS

We queried the National Cancer Database to identify patients treated for 1- to 2-cm ANETs from 2004 to 2018. Patients were stratified by surgical approach (appendectomy vs. hemicolectomy). Multivariable models were used to identify factors associated with the choice of surgical approach and the association between surgical approach and overall survival.

RESULTS

Of the 3,189 patients we included, 1,573 (49.3%) underwent right hemicolectomy and 1,616 (50.7%) appendectomy. The appendectomy rate increased from 37.7% in 2004 to 58.9% in 2018. On multivariable analysis, patients with grade 2 and 3 tumors were less likely to undergo appendectomy alone (odds ratio = 0.41, 95% confidence interval = 0.26-0.66). Longer travel distance was associated with a higher likelihood of undergoing appendectomy (odds ratio = 2.52, 95% confidence interval = 1.15-5.51). After adjusting for tumor grade, appendectomy alone had similar survival to hemicolectomy (hazard ratio = 1.03, 95% confidence interval = 0.67-1.59).

CONCLUSION

In this updated analysis of the National Cancer Database, right hemicolectomy was not associated with improved overall survival compared to appendectomy alone for 1- to 2-cm neuroendocrine tumors of the appendix. Although patients with grade 2 or 3 tumors are more likely to undergo right hemicolectomy, this procedure may not improve their treatment or overall outcome.

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.

Hemicolectomy versus appendectomy for patients with appendiceal neuroendocrine tumours 1-2 cm in size: a retrospective, Europe-wide, pooled cohort study

BACKGROUND

Awareness of the potential global overtreatment of patients with appendiceal neuroendocrine tumours (NETs) of 1-2 cm in size by performing oncological resections is increasing, but the rarity of this tumour has impeded clear recommendations to date. We aimed to assess the malignant potential of appendiceal NETs of 1-2 cm in size in patients with or without right-sided hemicolectomy.

METHODS

In this retrospective cohort study, we pooled data from 40 hospitals in 15 European countries for patients of any age and Eastern Cooperative Oncology Group performance status with a histopathologically confirmed appendiceal NET of 1-2 cm in size who had a complete resection of the primary tumour between Jan 1, 2000, and Dec 31, 2010. Patients either had an appendectomy only or an appendectomy with oncological right-sided hemicolectomy or ileocecal resection. Predefined primary outcomes were the frequency of distant metastases and tumour-related mortality. Secondary outcomes included the frequency of regional lymph node metastases, the association between regional lymph node metastases and histopathological risk factors, and overall survival with or without right-sided hemicolectomy. Cox proportional hazards regression was used to estimate the relative all-cause mortality hazard associated with right-sided hemicolectomy compared with appendectomy alone. This study is registered with ClinicalTrials.gov, NCT03852693.

FINDINGS

282 patients with suspected appendiceal tumours were identified, of whom 278 with an appendiceal NET of 1-2 cm in size were included. 163 (59%) had an appendectomy and 115 (41%) had a right-sided hemicolectomy, 110 (40%) were men, 168 (60%) were women, and mean age at initial surgery was 36·0 years (SD 18·2). Median follow-up was 13·0 years (IQR 11·0-15·6). After centralised histopathological review, appendiceal NETs were classified as a possible or probable primary tumour in two (1%) of 278 patients with distant peritoneal metastases and in two (1%) 278 patients with distant metastases in the liver. All metastases were diagnosed synchronously with no tumour-related deaths during follow-up. Regional lymph node metastases were found in 22 (20%) of 112 patients with right-sided hemicolectomy with available data. On the basis of histopathological risk factors, we estimated that 12·8% (95% CI 6·5 -21·1) of patients undergoing appendectomy probably had residual regional lymph node metastases. Overall survival was similar between patients with appendectomy and right-sided hemicolectomy (adjusted hazard ratio 0·88 [95% CI 0·36-2·17]; p=0·71).

INTERPRETATION

This study provides evidence that right-sided hemicolectomy is not indicated after complete resection of an appendiceal NET of 1-2 cm in size by appendectomy, that regional lymph node metastases of appendiceal NETs are clinically irrelevant, and that an additional postoperative exclusion of metastases and histopathological evaluation of risk factors is not supported by the presented results. These findings should inform consensus best practice guidelines for this patient cohort.

FUNDING

Swiss Cancer Research foundation.

Preoperative prediction of malignancy and surgical treatment strategy in appendiceal tumors: multicenter review of 51 consecutive cases

PURPOSE

A diagnostic and treatment strategy for appendiceal tumors (ATs) has not been established. We aimed to evaluate our treatment strategy in ATs, including laparoscopic surgery (LS), and to identify preoperative malignancy predictors.

METHODS

A total of 51 patients between 2011 and 2021 were retrospectively reviewed. Data, including tumor markers and imaging findings, were compared between carcinoma and non-carcinoma patients. Validity of planned operation was evaluated based on pathological diagnosis.

RESULTS

Twenty-five patients were diagnosed with carcinoma, 13 with low-grade mucinous neoplasm, and 13 with other diseases. Symptoms were more commonly present in carcinoma patients than in non-carcinoma patients (68.0% vs. 23.1%, p = 0.001). Elevated CEA and CA19-9 were more frequently observed in carcinoma patients than in non-carcinoma patients (p < 0.01 and p = 0.04, respectively). Five carcinoma patients had malignancy on biopsy, compared with zero non-carcinoma patients. Significant differences were noted in the percentages of carcinoma and non-carcinoma patients with solid enhanced mass (41.7% vs. 0%, p < 0.001) and tumor wall irregularity (16.7% vs. 0%, p = 0.03) on imaging. Although the sensitivity was not high, the specificity and positive predictive value of these findings were 100%. Forty-two patients (82.4%) underwent LS as minimally invasive exploratory and/or radical operation, of whom 2 were converted to open surgery for invasion of adjacent organ. No patients had intraoperative complications or postoperative mortality.

CONCLUSION

Clinical symptoms, elevated tumor markers, and worrisome features of solid enhanced mass and tumor wall irregularity on imaging can be malignancy predictors. For management of ATs, LS is feasible and useful for diagnosis and treatment.

Management of Appendix Neuroendocrine Neoplasms: Insights on the Current Guidelines

Appendiceal neuroendocrine neoplasms (ANENs) usually present as incidental findings at the time of appendectomy for acute appendicitis. They are rare, accounting for only 0.5-1% of intestinal neoplasms; they are found in 0.3-0.9% of all appendectomy specimens. They are usually sporadic tumors. There are several histological types including well-differentiated neuroendocrine tumors (NETs), poorly differentiated neuroendocrine carcinomas (NECs), and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs). Histologic differentiation and the grade of well-differentiated NETs correlate with clinical behavior and prognosis. Management varies based on differentiation, aggressiveness, and metastatic potential. There is debate about the optimal surgical management for localized appendiceal NETs that are impacted by many factors including the tumor size, the extent of mesoappendiceal spread, lymphovascular invasion and perineural involvement. In addition, the data to guide therapy in metastatic disease are limited due to the paucity of these tumors. Here, we review the current advances in the management of ANENs within the context of a multidisciplinary approach to these tumors.

Comprehensive Clinical Analysis of Gallbladder Neuroendocrine Neoplasms: A Large-Volume Multicenter Study During One Decade

BACKGROUND

This study aimed to comprehensively investigate the clinicopathologic characteristics and therapeutic situations of gallbladder neuroendocrine neoplasms (GB-NENs) in the real world via a multicenter, large-scale cohort study.

METHODS

The study searched for patients in 143 hospitals in China and enrolled 154 patients with GB-NENs diagnosed in 40 hospitals between 2004 and 2021. Clinicopathologic characteristics and therapeutic approaches were analyzed retrospectively.

RESULTS

The median age at the initial diagnosis of the patients with GB-NENs was 63 years (range 33-83 years), and 61.7% of the patients were women. Tumor-node-metastasis staging classified 92 patients as stage 3 or above. Based on the 2019 World Health Organization classification, 96 cases (62.3%) were confirmed pathologically as poorly differentiated neuroendocrine carcinomas, 13 cases (8.4%) as well-differentiated neuroendocrine tumors, and 45 cases as mixed neuroendocrine-non-neuroendocrine neoplasms. The liver was the most frequent metastatic site. Immunohistochemistry showed that synaptophysin was most frequently positive (80.4%), followed by chromogranin A (61.7%), and CD56 (58.4%). Computed tomography and magnetic resonance imaging showed more common clear boundaries (25/39 cases) and invasive growth features (27 cases). None of these cases had an accurate diagnosis before surgery, with a misdiagnosis rate of 100%. Surgical resection is the main treatment, and platinum-based chemotherapeutic regimens were preferred as adjuvant therapies for patients with GB-NENs. The available survival data for 74 patients showed an overall survival rate of 59% at 1 year, 33% at 3 years, and 29% at 5 years. No significant difference was found between the patients treated with and those treated without adjuvant chemotherapy.

CONCLUSIONS

Gallbladder neuroendocrine neoplasms have high malignancy and a poor prognosis. Importantly, this large-scale cohort study significantly improves our understanding of GB-NENs and will benefit the exploration of its mechanism and treatment modes. Further investigation is necessary to explore the management of this disease.

Surgical Treatment of Neuroendocrine Tumors of the Terminal Ileum or Cecum: Ileocecectomy Versus Right Hemicolectomy

BACKGROUND

Simple ileocecectomy and right hemicolectomy are two potential operative approaches to treat patients with neuroendocrine neoplasm in the terminal ileum and/or cecum (IC-NENs). We sought to define the long-term outcome of patients undergoing ileocecectomy versus right hemicolectomy for IC-NENs, as well as characterize number of nodes evaluated and lymph node metastasis (LNM) associated with each procedure.

METHODS

Patients who underwent curative-intent resections for IC-NENs between 2000 and 2016 were identified from a multi-institutional database. The clinicopathologic characteristics, surgical procedures, and the overall (OS) and recurrence-free survival (RFS) were compared among patients who underwent formal right hemicolectomy versus ileocecectomy only.

RESULTS

Among 127 patients with IC-NENs, median size of the largest tumor size was 2.0 (IQR 1.2-2.9) cm; 35 (27.6%) patients had multiple lesions. At the time of surgery, 93 (73.2%) patients underwent a right hemicolectomy, whereas 34 (26.8%) had ileocecectomy only. Every patient had a lymph node dissection (LND) with a median number of 16 (IQR 12-22) nodes evaluated. A majority (n = 110, 86.6%) of patients had LNM with a median number of 3 (IQR 2-5) LNM. Patients who underwent hemicolectomy had more lymph nodes evaluated versus patients who had an ileocecectomy only (median, 18 vs. 14, p = 0.004). Patients who underwent formal right hemicolectomy versus ileocecectomy had a similar OS (median OS, 101.9 vs. 144.5 months, p = 0.44) and RFS (median RFS, 70.3 vs. not attained, p = 0.80), respectively.

CONCLUSIONS

Ileocecectomy had similar long-term outcomes versus right hemicolectomy in treatment of IC-NENs despite a difference in the lymph node harvest.

Appendiceal Well-Differentiated Neuroendocrine Tumors: A Single-Center Experience and New Insights into the Effective Use of Immunohistochemistry

Background. Appendiceal well-differentiated neuroendocrine tumor is the most common histological type of appendiceal tumor. The majority of tumors are found incidentally at the tip of the appendix, with few exceptions. Due to its primarily indolent nature, this entity presents unique pathological challenges, particularly in the appropriate use of immunohistochemistry which this study aims to clarify. Patients and methods. Patients diagnosed at University Health Network (Canada) between 2005–2019 were selected and reviewed. Results. We identified 70 patients and sex distribution was female 60%; median age 36.5 years. Among them, 63 patients underwent appendectomy, and seven had initial right hemicolectomy for non-appendix lesions. Mean tumor size was 5.0 mm. Tumor extent was submucosa (15%); muscularis propria (34%); subserosa or mesoappendix (42%); visceral peritoneum (8%). All were clinically non-functional and negative for nodal and distant metastasis. Ninety percent of tumors were WHO Grade 1; 10% were WHO Grade 2. Immunohistochemically, an average of six stains were performed per patient. Nearly all tumors were positive for chromogranin A, synaptophysin, CAM5.2, and CDX2. MIB-1 staining was < 3% in 58/63 tumors. Other immunohistochemical stainings performed were hormonal markers (serotonin, glucagon, pancreatic peptide, peptide YY). Subsequent right hemicolectomy was performed on five patients. All were followed up (median 4 years 8 months), and all were alive without recurrence except for one patient who died of another comorbidity. Conclusion. Tumors that are small, localized, and of low grade can be reasonably exempt from an extensive immunohistochemical panel in the absence of non-typical clinical and morphological features.

Management of incidentally discovered appendiceal neuroendocrine tumors after an appendicectomy

Appendiceal neuroendocrine tumors (aNETs) are an uncommon neoplasm that is relatively indolent in most cases. They are typically diagnosed in younger patients than other neuroendocrine tumors and are often an incidental finding after an appendectomy. Although there are numerous clinical practice guidelines on management of aNETs, there is continues to be a dearth of evidence on optimal treatment. Management of these tumors is stratified according to risk of locoregional and distant metastasis. However, there is a lack of consensus regarding tumors that measure 1-2 cm. In these cases, some histopathological features such as size, tumor grade, presence of lymphovascular invasion, or mesoappendix infiltration must also be considered. Computed tomography or magnetic resonance imaging scans are recommended for evaluating the presence of additional disease, except in the case of tumors smaller than 1 cm without additional risk factors. Somatostatin receptor scintigraphy or positron emission tomography with computed tomography should be considered in cases with suspected residual or distant disease. The main point of controversy is the indication for performing a completion right hemicolectomy after an initial appendectomy, based on the risk of lymph node metastases. The main factor considered is tumor size and 2 cm is the most common threshold for indicating a colectomy. Other factors such as mesoappendix infiltration, lymphovascular invasion, or tumor grade may also be considered. On the other hand, potential complications, and decreased quality of life after a hemicolectomy as well as the lack of evidence on benefits in terms of survival must be taken into consideration. In this review, we present data regarding the current indications, outcomes, and benefits of a colectomy.

Nordic guidelines 2021 for diagnosis and treatment of gastroenteropancreatic neuroendocrine neoplasms

BACKGROUND

The diagnostic work-up and treatment of patients with gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN) has undergone major advances and new methods are introduced. Furthermore, an update of the WHO classification has resulted in a new nomenclature for GEP-NEN that is implemented in the clinic.

AIM

These Nordic guidelines summarise the Nordic Neuroendocrine Tumour Group's current view on how to diagnose and treat GEP-NEN patients and aims to be useful in the daily practice for clinicians.