Current size criteria for the management of neuroendocrine tumors of the appendix: are they valid? Clinical experience and review of the literature

Evaluation of immunohistochemical expression of novel neuroendocrine marker INSM1 and histological tumor growth pattern in well-differentiated neuroendocrine tumors of the appendix: 15-year single tertiary center experience

INTRODUCTION

Well-differentiated neuroendocrine tumors of the appendix (A-WDNET) are the most common neoplasms of the appendix but are rare and incidental. INSM1 is a novel transcription factor marker with high sensitivity and specificity for neuroendocrine differentiation. It may display architecturally diverse tumor growth patterns including solid, nest, insular trabecular, and acinar.

AIMS

The aim of this study was to determine the staining expression of INSM1 in A-WDNETs and detail the morphological tumor growth patterns.

MATERIALS AND METHODS

INSM1 immunohistochemistry was performed on 35 A-WDNET patients. Tumors were histologically classified according to their growth patterns.

RESULTS

Thirty-five patients, 60% of whom were male, had a mean age of 30 years at diagnosis and a mean tumor size of 0.9 cm. Eight percent of the tumors invaded the mucosa/submucosa, 34.3% showed invasion into the muscularis propria, 57.1% showed invasion into the subserosa or mesoappendix, LN metastasis was observed in two patients, lymph-vascular invasion in two patients, and perineural invasion in five patients. Ninety-four percent of the tumors were grade 1, the mitotic rate was >2% in two cases, and Ki-67 PI was >3% in two cases. INSM1 was positive in all cases (100%), 1+ 8.6%, 2+ 5.7%, 3+ 17.1%, 4+ 68.6%, weak staining in 11.4%, moderate staining in 22.9%, and strong staining in 67.7%. Type A histological growth pattern was observed in 54.3%, type B in 31.4%, and type C in 14.3% architecturally.

CONCLUSIONS

INSM1 was positive in all A-WDNET morphological patterns and was 100% sensitive. INSM1 IHC can be used as an alternative to traditional neuroendocrine markers or in combination with the diagnosis of neuroendocrine tumors.

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.

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).

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.

An Update on Appendiceal Neuroendocrine Tumors

The mainstay of appendiceal neuroendocrine neoplasm (aNEN) treatment is surgery, based on simple appendectomy or right-sided hemicolectomy with lymphadenectomy (RHC). The majority of aNENs are adequately treated with appendectomy, but current guidelines have poor accuracy in terms of selecting patients requiring RHC, especially in aNENs 1-2 cm in size. Simple appendectomy is curative for appendiceal NETs (G1-G2) < 1 cm (if the resection status is R0), whereas RHC with lymph node dissection is recommended in tumors ≥ 2 cm in diameter, based on the high risk of nodal metastases in these cases. The clinical management of aNENs 1-2 cm in size is more controversial because lymph node or distant metastases are uncommon but possible. In our opinion, patients with tumor size > 15 mm or with grading G2 (according to WHO 2010) and/or lympho-vascular invasion should be referred for radicalization with RHC. However, decision-making in these cases should include discussion within a multidisciplinary tumor board at referral centers with the aim of offering each patient a tailored treatment, also considering that relatively young patients with long-life expectancy represent the majority of cases.

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.

Neuroendocrine neoplasms of the lung and gastrointestinal system: convergent biology and a path to better therapies

Neuroendocrine neoplasms (NENs) can develop in almost any organ and span a spectrum from well-differentiated and indolent neuroendocrine tumours (NETs) to poorly differentiated and highly aggressive neuroendocrine carcinomas (NECs), including small-cell lung cancer (SCLC). These neoplasms are thought to primarily derive from neuroendocrine precursor cells located throughout the body and can also arise through neuroendocrine transdifferentiation of organ-specific epithelial cell types. Hence, NENs constitute a group of tumour types that share key genomic and phenotypic characteristics irrespective of their site of origin, albeit with some organ-specific differences. The establishment of representative preclinical models for several of these disease entities together with analyses of human tumour specimens has provided important insights into crucial aspects of their biology with therapeutic implications. In this Review, we provide a comprehensive overview of the current understanding of NENs of the gastrointestinal system and lung from clinical and biological perspectives. Research on NENs has typically been siloed by the tumour site of origin, and a cross-cutting view might enable advances in one area to accelerate research in others. Therefore, we aim to emphasize that a better understanding of the commonalities and differences of NENs arising in different organs might more effectively inform clinical research to define therapeutic targets and ultimately optimize patient care.

Clinical and pathologic characteristics of appendiceal neuroendocrine neoplasms diagnosed during pregnancy

INTRODUCTION

Although appendicitis occurs in approximately 1:1000 pregnancies, appendiceal neuroendocrine neoplasm (ANEN) diagnosis during pregnancy is very rare. Data on presentation, treatment and prognosis is scarce.

AIM

To describe ANEN cases diagnosed during pregnancy.

MATERIALS AND METHODS

A retrospective appraisal of 7 consecutive ANEN patients diagnosed during pregnancy from four Israeli tertiary medical centers and comparison with 17 cases described in the literature from 1965-2021.

RESULTS

Age at ANEN diagnosis was 26.4 ± 3.5 years (range 21-33). Patients were diagnosed between gestational weeks 6-40, most frequently in the third trimester (53%). The most common presenting symptom was abdominal pain. Tumor size was 14.3 ± 8.9mm (range 3-45mm). In patients from our series appendiceal base involvement was reported in 2/7; mesoappendiceal invasion in 5/7; lympho-vascular invasion in 2/7. Ki67 staining was reported in 6/7 cases and ranged from 1-10%. Pathology details were lacking in most of the previously published cases. All 7 pregnancies in our series resulted in term delivery with no complications, whereas in historical cases there were one first trimester abortion, one ectopic pregnancy, and one stillbirth. Right hemicolectomy was performed in 5/7 patients in our series and reported in 2/17 historical cases. All hemicolectomies were performed after delivery, 3-16 months after appendectomy. Local metastases were reported in two cases. Follow-up duration was 7-98 months for our patients and 3-48 months in 5 historical cases. No disease recurrence, distant metastases or mortality were noted.

CONCLUSIONS

To the best of our knowledge, this is the largest series describing the extremely rare diagnosis of ANEN during pregnancy. Although pathologic characteristics varied, pregnancy outcomes were usually favorable and long-term prognosis was excellent. This data may suggest that a conservative approach to patients with ANEN diagnosis during pregnancy can be considered.

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.

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.

"The past is a different country, they do things differently there": using the SEER data-base to assess prognosis in neuroendocrine tumours

Neuroendocrine neoplasms (NENs) are still considered to be rare neoplasms, and their epidemiology has been classically studied in large population-based cancer registries. Besides the benefits and the limitations that a cancer registry may have for all the registered cancers, the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Programme, has a number of drawbacks for the study of NENs. The change in management of NENs, either from diagnostic or from therapeutic points of view, the role of the Ki-67 labelling index and introduction of sensitive functional imaging, along with the misclassification of the more benign types of NENs, are the main limitations of the prognostic ability of the SEER data-base, particularly when including older data.

Diagnosis and Surgical Treatment of Gastroenteropancreatic Neuroendocrine Neoplasms: A Literature Review

This review aimed to highlight the characteristics and surgical treatments of tumours, and answer questions regarding the assessment of gastrointestinal neuroendocrine neoplasms (NENs) and optimal therapy. NENs comprise tumours that can produce hormones and cause a secretory syndrome. The diagnostic method and accuracy differ depending on the site of occurrence; hence, the relevant scientific society has created NEN treatment guidelines for each organ. Gastroenteric pancreatic (GEP) NENs have been unified and classified together according to the 2019 World Health Organization classification. Treatment is based on complete tumour resection, and when metastatic or primary lesions cannot be completely resected, lesions and symptoms are treated. Except for surgery for NENs, chemotherapy, molecularly targeted drugs, transarterial chemoembolization, etc., have also been confirmed as treatments. GEP NEN treatment methods will continue to advance and change because of surgery and other advances in treatment and diagnostic methods.

An incidental finding of ANET in a patient with perforated appendix: A case report

Introduction and importance

Appendiceal neuroendocrine tumors (ANETs) are incidentally found in 0.2–0.7% of appendectomies for suspected appendicitis.

Case presentation

A 29-year-old female presented with pain in the right lower quadrant of her abdomen for the past 48 h. On emergency appendectomy for suspected acute appendicitis, a perforated appendix was found. Histopathological examination showed grade 1 (low) ANET.

Clinical discussion

Appendiceal neuroendocrine neoplasms (ANENs) are commonly found at the tip of the appendix and are treated with appendectomy alone. For few ANENs located at the base, or small tumors (≤2 cm) infiltrating the submucosa, the muscularis, the subserosa layer or the mesoappendix, right hemicolectomy is recommended. However, no guidelines have been established concerning patients with appendiceal perforation in case of ANENs.

Conclusion

Although rare, ANETs should be considered in the differential diagnosis of acute appendicitis. Since, ANETs are rarely diagnosed preoperatively, subsequent patient evaluation after appendectomy is crucial for management of the patient.

•

Appendiceal Neuroendocrine tumor (ANET) are incidentally found in 0.2–0.7% of appendectomies for suspected appendicitis.

•

ANETs are commonly found at the tip of the appendix and are treated with appendectomy alone.

•

Although rare, ANETs should be considered in the differential diagnosis of acute appendicitis.

•

Since, ANETs are rarely diagnosed preoperatively, subsequent patient evaluation after appendectomy is crucial.

•

The best management of ANETs in case of perforated appendicitis remains unclear.

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.

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.

Diagnosis and Management of Gastrointestinal Neuroendocrine Tumors: A Comprehensive Literature Review

Neuroendocrine tumors (NETs) are epithelial neoplasms with predominant neuroendocrine differentiation and the ability to synthesize and secrete variable hormones and monoamines. They are relatively rare, accounting for 2% of all malignancy cases in the United States. The most common system affected by NETs is the gastrointestinal tract. Clinical presentation depends on the organ being involved and the hormone being secreted. It can be variable from asymptomatic incidental findings on imaging to intestinal obstruction, or carcinoid syndrome (CS). Several biochemical testings are developed to help with the diagnosis of NETs including 5-hydroxyindoleacetic acid (5-HIAA) and chromogranin A (CgA). Computerized tomography (CT) scans and magnetic resonance imaging (MRI) are the most commonly used modalities to localize the primary tumor and evaluate for metastasis. However, radionuclide imaging using somatostatin receptor-based imaging techniques has improved accuracy to detect smaller neoplasm. Surgical removal is the mainstay of treatment for locoregional tumors. Several medical managements are available for non-respectable NETs which include SSAs, peptide receptor radionuclide therapy (PRRT), and platinum-based chemotherapy agents.

Incidental appendiceal mass as the only manifestation of endometriosis

Appendiceal endometriosis is a rare condition that remains difficult to diagnose preoperatively. Herein, we present a case of appendiceal endometriosis presenting as a neuroendocrine tumor. A 34-year-old Caucasian woman was found to have an appendiceal mass with a small fluid collection on routine transvaginal ultrasound. The patient denied any symptoms. Features were consistent with those of a neuroendocrine tumour of the appendix. Laparoscopic appendectomy followed by histopathology revealed endometriosis with negative cytology for malignant cells. Preoperative characteristics of appendiceal tumours in women of childbearing age should be further investigated. Establishing clinical and surgical guidelines is the key to avoid invasive procedures and related adverse outcomes.

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

INTRODUCTION

Neuroendocrine neoplasms (NEN) of the appendix are often incidentally discovered after appendectomy. Appropriate management is debated. The purpose was to characterize a cohort of 335 appendix NEN and evaluate the risk of recurrence.

METHODS

Retrospective collection of data from 335 patients referred to the Neuroendocrine Tumor Center at Rigshospitalet 2000-2019. Appendix goblet cell carcinoids and mixed neuroendocrine non-neuroendocrine neoplasms were excluded. Patients were followed until December 31st, 2019. No patients were lost to follow-up.

RESULTS

Sixty-three percent of the patients were female. The median (range) age at diagnosis was 34 (9-92) years. Median follow-up was 66 (1-250) months. Median tumor size was 7 (1-45) mm with 10 (3%) tumors >20 mm. In 18 specimens (5%) resection margins were positive. Mesoappendiceal invasion was found in 113 (35%). Sixty-three (19%) patients underwent right-sided completion hemicolectomy (RHC) after appendectomy according to ENETS guidelines. Among these, 11 (17%) had lymph node metastases in the resected tissue. Further, one patient who underwent initial RHC due to colonic adenocarcinoma had lymph node metastases. All lymph node metastases were detected in patients with serotonin positive tumors. No patients with glucagon positive tumors (n = 85) had lymph node metastases. Mesoappendiceal invasion >3 mm and positive resection margins were associated with presence of lymph node metastases. No recurrences were recorded.

CONCLUSION

Following ENETS guidelines may lead to overtreatment of patients with respect to completion RHC. The risk of over- and undertreatment needs to be further evaluated.

Surgical treatment for gastrointestinal neuroendocrine tumors

Neuroendocrine tumors (NETs) are rare neoplasms, with an estimated annual incidence of 6.9/100 000. They arise from cells of the diffuse endocrine system, which are mainly dispersed throughout the gastrointestinal (GI), pancreatic, and respiratory tracts. The incidence of GI-NETs has recently begun to show a steady increase. According to the Surveillance, Epidemiology, and End Results database, 53% of patients with NETs present with localized disease, 20% with locoregional disease, and 27% with distant metastases at the time of diagnosis. Surgery is the mainstay for the treatment of locoregional GI-NETs. Endoscopic resection is an option for well-differentiated early GI-NETs, which are thought to very rarely metastasize to lymph nodes. A lesion that is technically difficult to resect via endoscopy is an indication for local resection (partial resection without lymph node dissection). GI-NETs with possible lymph node metastasis is an indication for enterectomy with lymph node dissection. For NETs with metastatic lesions, cytoreduction surgery can control hormonal hypersecretion and alleviate symptoms; therefore, cytoreduction surgery is recommended. The indications for surgery vary and are based on the organ where the NET arose; therefore, an understanding of the patient's clinical state and individualized treatment that is based on the characteristics of the patient's GI-NET is needed. This review summarizes surgical treatments of GI-NETs in each organ.

The impact of lymph node metastases and right hemicolectomy on outcomes in appendiceal neuroendocrine tumours (aNETs)

INTRODUCTION

European Neuroendocrine Tumour Society (ENETS) recommends managing appendiceal neuroendocrine tumours (aNET) with appendicectomy and possibly completion right hemicolectomy (CRH). However, disease behaviour and survival patterns remain uncertain.

MATERIALS AND METHODS

We retrospectively assessed the impact of lymph nodes and CRH on outcomes, including survival, in all aNET patients diagnosed between 1990 and 2016.

RESULTS

102 patients (52F, 50 M), median age 39.4 (range 16.3-81.1) years, were diagnosed with aNET. Mean tumour size was 12.7 (range 1-60) mm, most sited in appendiceal tip (63%). Index surgery was appendicectomy in 79% of cases while the remainder underwent colectomy. CRH performed in 30 patients at a median 3.2 (range 1.4-9.8) months post-index surgery yielded residual disease in nine: lymph nodes (n = 8) or residual tumour (n = 1). Univariate logistic regression showed residual disease was significantly predicted by tumour size ≥2 cm (p = 0.020). Four patients declined CRH, but did not suffer relapse or reduced survival. One patient developed recurrence after 16.5 years of follow-up and another patient developed a second neuroendocrine tumour after 18.8 years follow-up. There were 5 deaths; one being aNET-related. 5-year and 10-year overall survival were 99% and 92% respectively; 5-year and 10-year relapse-free survival were 98% and 92% respectively. Only 5-year relapse-free survival was affected by ENETS stage (p = 0.002).

CONCLUSION

aNETs are indolent with very high rates of overall and relapse-free survival. Recurrence is rare, and in this series only occurred decades later, making a compelling case for selective surveillance and follow-up. The significance of positive lymph nodes and the necessity for completion right hemicolectomy remain unclear.

Management of Appendiceal Neuroendocrine Tumors: Metastatic Potential of Small Tumors

BACKGROUND

Appendiceal neuroendocrine tumors (ANETs) are rare neoplasms usually discovered incidentally during appendectomy. ANETs < 2 cm were thought to have no metastatic potential, and this dogma has driven management. Our aim is to evaluate the metastatic potential of ANETs < 2 cm.

PATIENTS AND METHODS

A retrospective review was performed in a series of patients with ANETs who presented to our tertiary referral center from 1998 to 2019. Demographics, tumor characteristics, treatment, and clinical outcomes were evaluated.

RESULTS

In total, 114 patients were included. Median follow-up was 3.3 years (range, 21 days-15 years). At last follow-up, 34 (30%) patients had positive regional lymph nodes and 20 (18%) patients had metastatic disease. Of the 20 patients with metastatic disease, 11 (55%) had primary ANETs < 2 cm. Patient age > 40 years at diagnosis and ANETs with serosal invasion, lymphovascular invasion, intermediate tumor grade, or positive lymph nodes were features significantly more likely to present with metastatic disease. We found no difference in the rate of lymph node positivity, metastatic disease, or overall survival when patients were stratified by tumor size or type of resection (appendectomy vs. right hemicolectomy). On multivariate analysis, patients with metastatic disease at diagnosis had worse overall survival (HR = 24.4, p = 0.008).

CONCLUSIONS

In our cohort, tumor size was not a significant risk factor for metastatic disease or worse outcome as many patients with ANETs < 2 cm developed metastatic disease. Appendectomy alone was sufficient surgical management for most ANETs. Patients with risk factors for metastatic disease, regardless of primary ANET size, should be evaluated thoroughly and counseled for further management and surveillance.

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.

Histopathological diagnosis of appendiceal neuroendocrine neoplasms: when to perform a right hemicolectomy? A systematic review and meta-analysis

PURPOSE

The European Neuroendocrine Tumor Society (ENETS) guidelines advocate a right hemicolectomy (RHC) only in patients with appendiceal neuroendocrine neoplasms (aNENs) at risk for N+(node positive). The risk is defined using site, size, and grading of tumor as well as mesoappendiceal or lymphovascular invasion.

METHODS

A systematic review and meta-analysis was carried out. The data were reported using risk difference (RD) to define the risk of N+. The number needed to treat/harm (NNT/NNH) and the likelihood of being helped or harmed (LHH) were calculated using RD. Two strategies were considered: "to treat all" versus "to treat only patients having aNENs with risk stigmata". The aim was to evaluate the harm/benefit ratio related to the use of the ENETS lymph-nodal metastases (N+) risk factors.

RESULTS

Six studies were included involving a total of 261 patients. The RD (-0.30; P < 0.001) of N+ was significantly lower in aNENs ≤ 20 mm as compared to those >20 mm. One unnecessary RHC every five patients (NNT = 5) could be avoided while 1 patient with N+ every six patients (NNH = 6) remained untreated. The risk was lower than the benefits (LHH = 1.2). The RD NNT, NNH, and LHH values suggested that only a 15 mm cutoff and the presence of lymphovascular invasion could be considered useful.

CONCLUSIONS

An RHC should be performed in patients with aNENs >20 mm. The use of a 15 mm cutoff criterion had a similar outcome to that of a 20 mm cutoff. Lymphovascular invasion should only be considered a minor criterion. Selection based on other parameters should be avoided.

Unmet Needs in Appendiceal Neuroendocrine Neoplasms

Appendiceal neuroendocrine neoplasms (ANEN) are mostly discovered coincidentally during appendicectomy and usually have a benign clinical course; thus, appendicectomy alone is considered curative. However, in some cases, a malignant potential is suspected, and therefore additional operations such as completion right hemicolectomy are considered. The existing European Neuroendocrine Tumour Society (ENETS) guidelines provide useful data about epidemiology and prognosis, as well as practical recommendations with regards to the risk factors for a more aggressive disease course and the indications for a secondary operation. However, these guidelines are based on heterogeneous and retrospective studies. Therefore, the evidence does not seem to be robust, and there are still unmet needs in terms of accurate epidemiology and overall prognosis, optimal diagnostic and follow-up strategy, as well as identified risk factors that would indicate a more aggressive surgical approach at the beginning and a more intense follow-up. In this review, we are adopting a critical approach of the ENETS guidelines and published series for ANEN, focusing on the above-noted "grey areas".

Challenging the Current Risk Factors of Appendiceal Neuroendocrine Neoplasms: Can They Accurately Predict Local Lymph Nodal Invasion? Results from a Large Case Series

BACKGROUND

Appendiceal neuroendocrine neoplasms (ANEN) are uncommon entities, which run mostly an indolent course. Appendicectomy alone is usually curative, except for in a selected group of patients that are deemed to be at risk of loco-regional metastases, in whom a completion right hemicolectomy (RHC) is recommended. The current "Guidelines" criteria for the latter have been controversial, and may result in overtreatment, which is concerning for a young patient population.

OBJECTIVE

The aim of this study is to evaluate the prognostic value of the current criteria in identifying more accurately those at-risk patients.

METHODS

This was a retrospective study of the 263 cases of ANEN referred for advice or management to a tertiary referral unit over a 10-year period. Seventy-two patients underwent RHC, based on criteria, suggested by International Guidelines. Each one of those was assessed to identify whether it correlated with lymph node invasion (LNI) at the RHC surgical specimen.

RESULTS

Tumour grade (p < 0.001), vascular (p = 0.044) and lymph vessel invasion (p < 0.001) were all found to be statistically significant independent risk factors for LNI identified following RHC, whilst tumour size (p = 0.375) and mesoappendiceal invasion (MAI) (p = 0.317) were not statistically significant. However, deep MAI and tumour size >2 cm showed a correlation with each other on LNI positive subgroup analysis. Location in appendiceal base made LNI more likely but again was not significant (p = 0.133).

CONCLUSIONS

Higher tumour grade and lymphovascular invasion should be considered as the most important risk prognosticators. Surprisingly, tumour size was not found to be significant in our cohort. Further international multicentre studies with large numbers of patients are needed to fully validate those data.

Gastroenteropancreatic Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are heterogeneous malignancies arising from the diffuse neuroendocrine system. They frequently originate in the gastroenteropancreatic (GEP) tract and the bronchopulmonary tree, and their incidence has steadily increased in the last 3 decades. Fundamental biologic and genomic differences underlie the clinical heterogeneity of NETs, and distinct molecular features characterize NETs of different grades and different primary sites. Although surgery remains the cornerstone of treatment for localized tumors, systemic treatment options for patients with metastatic NETs have expanded considerably. Somatostatin analogs have demonstrated both antisecretory and antitumor efficacy. Peptide receptor radionuclide therapy with lutetium-177 dotatate (¹⁷⁷ Lu-DOTATATE) has been approved for advanced GEP-NETs. The antitumor activity of everolimus has been demonstrated across a wide spectrum of NETs, and the antiangiogenic agent sunitinib has been approved for pancreatic NETs (pNETs). Chemotherapy with temozolomide and capecitabine has recently demonstrated an unprecedented prolongation of progression-free survival in a randomized trial of pNETs. Multiple retrospective series have reported the efficacy of liver-directed therapies both for palliating symptoms of hormone excess and for controlling tumor growth. Telotristat, an oral inhibitor of tryptophan hydroxylase, has been shown to reduce diarrhea in patients with carcinoid syndrome. Defining the therapeutic algorithm and identifying biomarkers predictive of response to treatments are among the main priorities for the next decade of research in the NET field.

The Problem of Appendiceal Carcinoids

Appendiceal neuroendocrine neoplasms are uncommon, mostly discovered coincidentally during appendectomy. They usually show a benign clinical course and appendectomy alone is curative. However, some cases may harbor malignant potential; therefore, additional/prophylactic operations, such as right hemicolectomy, are offered. Current international guidelines are based on heterogeneous and retrospective series. Thus, there is lack of robust evidence, mainly in terms of accurate factors, that could identify patients at risk, requiring more extensive surgical treatment. In this article, we highlight controversies in the epidemiology, workup assessment, and management algorithms of appendiceal neuroendocrine neoplasms, but also to explore future developments and advances.

Novel nomogram combining depth of invasion and size can accurately predict the risk for regional nodal metastases for appendiceal neuroendocrine tumors (A-NET)

INTRODUCTION

The need for regional lymphadenectomy for treating appendiceal neuroendocrine tumors (A-NET) is determined by the risk of nodal metastasis. Current guidelines for A-NET are solely based on tumor size. Methods Patients with A-NET from 1988 to 2012 were identified from the SEER registry. The depth of invasion was defined as limited to the lamina propria (LP), invading the muscularis propria (MP), and through the serosa (TS).

RESULTS

A total of 418 patients were included; the majority were female, white, and node-negative. On univariate and multivariable, the risk of nodal metastasis was associated with age, size, depth of invasion, and extent of surgery. The model predicted the likelihood of nodal metastasis, with an area under the curve of 0.89. On survival analysis, age and tumor size predicted the survival in A-NET. In a Cox regression model, they continued to predict survival. These data were utilized to create a nomogram to predict the risk of nodal metastases.

CONCLUSION

This nomogram, accurately predicts the risk of regional nodal metastases in A-NET. In addition to providing valuable information on risk for regional nodal metastases, the depth of invasion is also predictive of survival for A-NET.

Neuroendocrine, goblet cell and mixed adeno-neuroendocrine tumours of the appendix: updates, clinical applications and the future

Appendiceal neuroendocrine neoplasms are rare, clinically challenging tumours that are typically incidentally diagnosed, have a poorly understood biology and have controversy surrounding their management. Most are adequately treated with appendectomy, and although distant metastases are rare, the threat of disease dissemination remains and current guidelines possess poor accuracy in terms of selecting patients requiring more extensive surgery, i.e. oncological right-hemicolectomy. Areas covered: In this article, we discuss the presentation and diagnostic work-up of patients with appendiceal neuroendocrine neoplasms, and also examine the evidence base for existing management strategies. We highlight controversies within the management of these tumours, and anticipate avenues for further progress. Although no longer classified as neuroendocrine neoplasms, we also discuss two related forms of tumours with neuroendocrine features - goblet cell cancers and mixed adeno-neuroendocrine carcinomas. Expert commentary: Existing guidelines for the treatment of appendiceal neuroendocrine neoplasms are derived from a limited evidence base and are unable to accurately predict which patients require extensive attempts at surgical disease control. Future advances in the field of improved patient selection for more extensive surgery may be possible with multi-factorial tumour assessment integrating morphological and molecular analyses.

Long-Term Survival is not Impaired After the Complete Resection of Neuroendocrine Tumors of the Appendix

BACKGROUND

Appendiceal neuroendocrine tumors (aNET) are a common entity in routine medical care, with a rate per appendectomy as high as 0.3-0.9 %. Considering the relatively young age at diagnosis for these patients, exact information about the long-term prognosis of aNET is required. Survival rates vary substantially between 71 and 100 % and are mostly limited to 5 years. This investigation assessed the long-term mortality rates of patients who underwent aNET resections at fifteen hospitals.

METHODS

Between 1990 and 2003, the 10-year survival rates of 79 patients were analyzed using risk-adjusted Cox proportional hazard regression models adjusted for population-based baseline mortality. Additionally, prognostic factors for the oncologic outcomes were assessed.

RESULTS

The median follow-up of all patients was 12.1 and 13.7 years for those alive. All patients underwent curative R0 resections. No distant metastases were diagnosed. A total of 31 (39.2 %), 29 (36.7 %), 18 (22.8 %), and 1 (1.3 %) patients had stage I, IIA, IIB, and IIIB aNET, respectively, according to the latest classification by the European Neuroendocrine Tumor Society. The 10-year overall and relative survival rates were 83.6 % (95 % CI 75.5-92.6 %) and 96.7 % (95 % CI 87.5-107 %), respectively. The 10-year relative survival rate after resection of aNET did not differ from the survival of the average national population with the same age and gender (p = 0.947). Second primary malignancies (hazard ratio of death 7.0, 95 % CI 1.6-30.6) were identified as a significant prognosticator for long-term survival.

CONCLUSIONS

Long-term survival is not significantly depreciated after the curative resection of aNET.

Clinical experience in appendiceal neuroendocrine neoplasms

AIM OF THE STUDY

To analyse the incidence of appendiceal neuroendocrine neoplasms in appendectomy specimens and establish the epidemiological and histopathological features, treatment, and clinical course.

MATERIAL AND METHODS

Between 2004 and 2013, 975 patients who underwent appendectomy in Ankara Oncology Education and Research Hospital were retrospectively analysed.

RESULTS

Neuroendocrine neoplasm was detected in the nine of 975 (0.9%) patients. Neuroendocrine neoplasms were diagnosed in eight patients by appendectomy, which was performed because of the prediagnosis of acute appendicitis, and in one patient by the suspicious mass detection during surgical procedures that were done in the appendix for a different reason. Eight of the patients' tumours were in the tip of the appendix, and one of the patients' tumours was at the base of appendix. Tumour size in 77.8% of patients was equal or less than 1 cm, in 22.2% patients it was 1-2 cm. There was tumour invasion in the muscularis propria layer in four patients, in the serosa layer in three patients, and in the deep mesoappendix in two patients. Patients were followed for a median of 78 months. In the follow-up of patients who were operated because of colon cancer, metachronous colon tumour evolved. This patient died due to progressive disease. Other patients are still disease-free.

CONCLUSIONS

The diagnosis of neuroendocrine neoplasm is often incidentally done after appendectomy. Tumour size is important in determining the extent of disease and in the selection of the surgical method during operation.

Appendiceal neuroendocrine neoplasms: diagnosis and management

Gastrointestinal neuroendocrine neoplasms (GI-NENs) are increasingly being recognised, while appendiceal NENs (aNENs) currently constitute the third most common GI-NEN. Appendiceal NENs are generally considered to follow an indolent course with the majority being localised at diagnosis. Thus, the initial surgical approach is not that of a planned oncological resection. Due to the localised nature of the disease in the majority of cases, subsequent biochemical and radiological assessment are not routinely recommended. Histopathological criteria (size, mesoappendiceal invasion, Ki-67 proliferation index, neuro- and angio-invasion) are mainly used to identify those patients who are also candidates for a right hemicolectomy. Goblet cell carcinoids are a distinct entity and should be treated as adenocarcinomas. Despite the absence of any substantial prospective data regarding optimal management and follow-up, recent consensus statements and guidelines have been published. The purpose of this review is to overview the published studies on the diagnosis and management of appendiceal NENs and to suggest a possible management protocol.

Perforation in appendiceal well-differentiated carcinoid and goblet cell tumors: impact on prognosis? A systematic review

BACKGROUND

Carcinoid tumors are the most common malignant lesions arising from Appendix and are mostly found incidentally during surgery for appendicitis. Perforation of Appendix occurs in 10-20% of cases with appendicitis. Currently, no guidelines exist for the treatment of perforated carcinoids of Appendix.

METHODS

A systematic literature search was performed to identify relevant articles on classical carcinoid or goblet cell carcinoid of Appendix in an attempt to evaluate the impact of perforation on management and prognosis. All articles on carcinoids reporting perforation of Appendix were included.

RESULTS

In total, 23 articles on carcinoid of Appendix with an associated perforation were found. Perforation was never investigated or mentioned as a possible negative factor on recurrence or prognosis. Among a total of 103 patients with classical carcinoids and associated perforation, no peritoneal recurrence or death was described, although follow-up data were often unspecified or scarce. Among a total of 18 goblet cell carcinoids with perforation, metastatic spread to the peritoneum was described in one case and two tumor-related deaths occurred among these cases. No specific relation to perforation could be distilled.

CONCLUSIONS

The best available evidence suggests that perforation has no influence on prognosis of classical appendiceal carcinoids. In contrast, peritoneal carcinomatosis is much more common in goblet cell carcinoids but the true impact of perforation remains unclear. Careful follow-up should therefore be considered in these cases.