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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.

AimAppendiceal neuroendocrine tumors (NETs) are rare NET that are often incidentally discovered following appendectomy performed for acute appendicitis. Herein, we report our institution’s experience regarding the management and long-term follow-up of appendiceal NETs.MethodThis study included patients who underwent appendectomy for acute appendicitis and were diagnosed with appendiceal NETs between 2011 and 2020. Patient data were retrospectively retrieved from the hospital computer system. Clinical information, demographic details, tumor size, localization within the appendix, histopathological findings, and surgical procedures were evaluated.ResultsThe study included data from 44 patients, with 22 men and 22 women, and a mean age of 31.1±12.7 years. All patients presented with symptoms consistent with acute appendicitis upon admission to the hospital. Tumors were distally located in 33 patients, centrally located in seven patients, and proximally located in four patients. Among the 44 patients included in the study, 42 underwent appendectomy, whereas two underwent primary right hemicolectomy during the initial surgery. One patient who underwent appendectomy required subsequent right hemicolectomy 3 weeks later. The mean follow-up duration was 5.4±2.5 years. During the follow-up period, metastasis was detected in only one patient with a tumor size larger than 2 cm located proximally. No recurrence or evidence of metastasis was observed in the remaining patients during long-term follow-up.ConclusionAccording to the results of this study, appendectomy may be sufficient for appendiceal NETs measuring <1 cm, and routine follow-up may not be necessary. For appendiceal NETs measuring 1-2 cm in diameter, further studies are needed to establish treatment protocols.

Episodic severe Cushing syndrome resulting from ectopic ACTH secretion (EAS) from appendiceal neuroendocrine tumor (NET) is extremely rare. Here, we describe a case of a 24-year-old woman with episodic severe EAS resulting from appendiceal NET with extensive metastatic disease. The patient presented with rapid weight gain, violaceous striae, fatigue, edema, and anxiety. Biochemical evaluation showed markedly elevated 24-hour urinary free cortisol greater than 10-fold above the upper limit of normal, and widely fluctuating peaks and troughs of serum cortisol and ACTH concentrations indicating episodic severe EAS. Surgery for primary malignancy was initially deferred because of the high risk of perioperative complications related to severe hypercortisolism. She underwent bilateral adrenalectomy as first-line definitive treatment for severe EAS. Four months after adrenalectomy, she underwent cytoreductive surgery for primary metastatic appendiceal NET. Subsequent peptide receptor radionuclide therapy and monthly lanreotide injections rendered her disease stable. Three years after the initial presentation, she continued to undergo active surveillance with maintenance lanreotide for residual but stable metastatic appendiceal neuroendocrine tumor. This case of a rare metastatic appendiceal NET with EAS demonstrates the importance of individualized management and highlights the need for consideration of prompt bilateral adrenalectomy for patients with severe Cushing syndrome.

Abstract Neuroendocrine tumors of the appendix are rare but clinically significant tumors, often discovered incidentally during surgical procedures or radiological investigations for other abdominal conditions. When they occur in association with an appendiceal mucocele, another uncommon entity characterized by abnormal dilation of the appendix due to mucus accumulation, these concurrent findings can present diagnostic and therapeutic challenges. Herein, we report the case of a 54-years-old female, previously diagnosed and treated for early-stage breast cancer. During routine surveillance, an abdominal ultrasound revealed a suspicious mass in the region of the appendix. The patient underwent abdominal computed tomography followed by abdominal magnetic resonance imaging, which demonstrated a heterogeneous mass in the right lower quadrant. The patient underwent an appendectomy and resection of the tumor.

Appendix neoplasms are rare tumors of the gastrointestinal system. Appendiceal adenocarcinoma, appendiceal mucinous neoplasm, and neuroendocrine tumors (NETs) are the most encountered appendix-related neoplasms. The patients are usually got diagnosed after histopathological examination. This study aimed to explore the epidemiology, pathological subtypes, and treatment modalities of appendix neoplasms. A retrospective examination was made with 2821 patients who underwent appendectomy between April 2010 and August 2020. Demographic, clinical, radiological, surgical findings, and histopathological results were collected from the patient files. Appendix neoplasms were detected in 1.06% of the patients included in the study. The mean age was 44.6±17.5 (17-83) years. Eight NETs, seven adenocarcinomas, fourteen mucinous neoplasms, and one neuroma were diagnosed with patients. Appendiceal neoplasms are generally asymptomatic and often diagnosed with postoperative histopathological ex-amination. If the result is adenocarcinoma, right hemicolectomy recommends. Treatment of NETs depends on factors such as tumor size, location, mesoappendix invasion, and lymph node involvement. In the presence of mucinous neoplasm, surgical intervention is determined according to the pathological subtype and involvement of mesoappendix. The need for additional surgical intervention or medical treatment for patients with tumor, histopathological results must be followed carefully after appendectomy.

Introduction: Appendiceal neuroendocrine neoplasms (aNENs) are the most common malignant appendiceal neoplasms. Localized aNENs are typically managed with an appendectomy; however, right colectomy may be necessary in patients with a high risk of nodal disease. However, the role of right hemicolectomy and the optimal surveillance strategy, particularly for tumors between 1 and 2 cm, remains controversial. Material and Methods: This retrospective, observational study evaluated patients diagnosed with aNENs between January 1995 and July 2015 at two tertiary centers in Ireland and Italy. Data were extracted from a prospectively maintained registry and included clinical, pathological, and therapeutic variables, as well as follow-up outcomes. Results: Forty-three patients (41.8% male; median age 27.5 years) were included, with a median follow-up of 49 months. The median tumor size was 6.4 mm (range: 0.6–40 mm). The majority were G1 tumors (58%), and staging distribution was predominantly Stage I (60%). While no significant differences in demographics or tumor features were observed between centers, completion right hemicolectomies were more frequent in the Irish cohort (p = 0.04). Follow-up practices varied, with more intensive imaging and biochemical monitoring observed in the Italian cohort. Overall prognosis was excellent, with a single case of recurrence during the study period. Conclusions: Most aNENs are effectively managed with appendectomy alone, and routine follow-up may be unnecessary in the absence of adverse pathological features. Accurate risk stratification, driven by comprehensive histopathological assessment, is critical for optimizing management and surveillance strategies.

Background Appendiceal neuroendocrine tumors (A-NETs) are rare neoplasms of the GI tract. They are typically managed according to tumor size; however, the impact of surgical strategy on the short- and long-term outcomes is unknown. Methods All patients who underwent resection of A-NET at 8 institutions from 2000 to 2016 were analyzed retrospectively. Patient clinicopathologic features and outcomes were stratified according to resection type. Results Of 61 patients identified with A-NET, mean age of presentation was 44.7 ± 16.0 years and patients were predominantly Caucasian (77%) and female (56%). Mean tumor size was 1.2 ± 1.3 cm with a median of 0.8 cm. Thirty-one patients (51%) underwent appendectomy and 30 (49%) underwent colonic resection. The appendectomy group had more T1 tumors (87% vs 42%, p < 0.01) than the colon resection group. Of patients in the colon resection group, 27% had positive lymph nodes and 3% had M1 disease. R0 resections were achieved in 90% of appendectomy patients and 97% of colon resection patients. Complications occurred with a higher frequency in the colon resection group (30%) compared with those in the appendectomy group (6%, p = 0.02). The colon resection group also had a longer length of stay, higher average blood loss, and longer average OR time. Median RFS and OS were similar between groups. Conclusion A-NET RFS and OS are equivalent regardless of surgical strategy. Formal colon resection is associated with increased length of stay, OR time, higher blood loss, and more complications. Further study is warranted to identify patients that are likely to benefit from more aggressive surgery.

Appendiceal neuroendocrine tumors (ANETs) are rare gastrointestinal malignancies that are often diagnosed incidentally during or after surgery for suspected appendicitis, presenting significant diagnostic challenges. Existing studies primarily focus on the epidemiology and management of ANETs but lack comprehensive analyses of diagnostic limitations and treatment outcomes. This study presents five cases of ANETs, emphasizing the ongoing challenges in preoperative diagnosis. Consistent with the medical literature, tumors smaller than 1 cm were effectively managed with appendectomy, whereas a larger tumor with high-risk features necessitated right hemicolectomy. Preoperative imaging consistently failed to identify the tumors, underscoring its limitations in detecting neoplastic causes of appendicitis. These findings highlight the need for larger-scale studies, the development of advanced imaging techniques—particularly with the integration of artificial intelligence—and standardized follow-up protocols for high-risk cases.

Introduction Acute appendicitis is significantly common. Despite the increased use of computed tomography, the number of perforated cases has been stable in the past three decades. Between 2% and 6% of patients with acute appendicitis present appendiceal mass, often described as inflammatory phlegmon or abscess. Malignant tumors are confirmed by pathological analysis in 0.9–1.4% of all appendectomies performed to treat acute appendicitis. However, recent series demonstrate an elevated incidence of malignancies, ranging from 5.9 to 12%, in patients with inflammatory appendiceal mass. Methods The analysis was based on a systematic review of the literature. The articles were searched in PubMed for the period from 1987 to 2016. Articles presenting the incidence of the hidden malignancy among patients with appendiceal inflammatory mass were selected. Variables as age, interval appendectomy rate, the incidence of neoplasm, time to surgery, minimally invasive assessment, histology, right colectomy rate and morbidity were analyzed. Results A total of 13.244 patients were described as presenting acute appendicitis. Appendiceal tumor is present in approximately 1% of the appendectomies, while the rate of neoplasm varies from 10 to 29% in patients presenting appendiceal inflammatory mass. Interval appendectomies, despite been the minority of the procedures, disregard the higher morbidity associated with right sided colectomies. The review of literature also describes oncologic, histologic and clinical aspects of patients presenting appendiceal neoplasm, describing the most frequent histologic subtypes of this illness. Conclusion Hidden appendiceal neoplasm in acute appendicitis are rare, fortunately. However, its incidence is much higher in patients presenting appendiceal inflammatory mass. Hence, interval appendectomy should be considered in this subgroup of patients.

Appendiceal neuroendocrine tumor (NET) is the most common type of appendiceal cancer and is rare in the pediatric population. The clinical characteristics of this cancer are not specific and are highly similar to those of acute appendicitis. By contrast, acute appendicitis is a common surgical indication that is caused by obstruction of the appendix lumen. With a detection rate of 0.5-1% in all appendectomy specimens, appendiceal NET is rare histopathologically and can easily be missed. However, detecting an appendiceal NET in a patient with appendicitis is highly difficult. Therefore, clinicians must be aware of this much under-reported and rare tumor in children. In the present report, a case was reported, of a 13-year-old female child who initially presented with clinical presentation of acute appendicitis, but was subsequently diagnosed with appendiceal NET by histopathological examination after an emergency appendectomy. Follow-up examination including abdominal enhanced CT and enteroscopy 2 years after surgery revealed normal results.