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Background: Acute appendicitis is one of the most common surgical emergencies. With antibiotic-first treatment strategies gaining importance, the risk of an appendiceal tumor as an incidental finding or as the cause of appendicitis presents an obstacle to a conservative approach. Neuroendocrine tumors, the most frequent type of appendiceal tumors, are difficult to diagnose preopera-tively due to their small size. This study aims to identify predictive factors for neuroendocrine tumors in patients undergoing surgery for acute appendicitis by analyzing imaging and clinical characteristics, thereby enhancing preoperative diagnostic accuracy and guiding surgical interventions., Methods: This retrospective observational study included 1,298 patients who underwent appendectomy from January 2014 to May 2024. After excluding 59 patients with normal pathology results, 40 with variable pathologies, and 49 with inaccessible computed tomography (CT) images, 1,150 patients remained (1,135 with acute appendicitis and 15 with neuroendocrine tumors). Abdominal CT scans were evaluated for appendiceal diameter, wall thickness, cecal wall thickness, periappendiceal fat stranding, fluid collection, lymphadenopathy, intraluminal and free periappendiceal air, mucosal hyperenhancement, the presence of appendicolith, mural calcification, and mural nodules., Results: The presence of a mural nodule protruding into the lumen was significantly higher in neuroendocrine tumor patients compared to those with acute appendicitis, with a sensitivity of 53.3%, specificity of 95.8%, positive predictive value (PPV) of 31.9%, negative predictive value (NPV) of 99.4%, and accuracy of 97.9%. Intraluminal air was also more frequent in neuroendocrine tumor patients, with a sensitivity of 53.3%, specificity of 76.7%, PPV of 2.9%, NPV of 99.2%, and accuracy of 76.4%. Other imaging parameters did not show significant differences between the two groups., Conclusion: This study identifies mural nodules and intraluminal air as significant predictors of neuroendocrine tumors in patients with acute appendicitis, emphasizing the importance of meticulous preoperative imaging evaluations. Incorporating these predictors into diagnostic protocols could improve the preoperative identification of neuroendocrine tumors, enabling more appropriate surgical interventions. Future research should validate these findings through prospective studies and explore advanced imaging techniques to further enhance the detection of appendiceal neoplasms, ultimately improving patient outcomes and reducing overlooked malignancies.

A 71-year-old woman was found to have submucosal tumor-like lesion on colonoscopy (CS) before gastric surgery, and computed tomography (CT) showed a 12-mm structure at the base of the appendix. The lesion could not be clearly detected on CT nine months later, but it had enlarged again on CT one year later; therefore, CS and endoscopic ultrasound (EUS) were performed. The lesion was determined to be cystic with viscous contents, and laparoscopic appendicectomy was performed. This is the first report of low-grade appendiceal mucinous neoplasm (LAMN) diagnosed by a histopathologic examination of a resected specimen showing shrinkage and re-expansion of the appendix.

A 63-year-old woman was admitted to our hospital with suspected appendicitis. Abdominal CT revealed an enlarged appendix, and findings consistent with some small nodules. She was diagnosed with appendicitis and successfully treated with antibiotics. Contrast-enhanced CT performed 2 months after discharge revealed a reduction in small nodules, and tumor markers were not elevated. Therefore, we concluded that this case was unlikely to be an appendiceal tumor. Interval appendectomy was performed laparoscopically, and histopathological analysis revealed a low-grade appendiceal mucinous neoplasm(LAMN). Herein, we present this case and review the relevant literature.

We encountered a rare case of appendiceal carcinoma associated with Amyand's hernia, which was difficult to diagnose preoperatively. A 74-year-old man presented to our hospital with right lower abdominal pain. A hard mass was palpable in the right lower abdomen, and blood tests showed a slightly elevated inflammatory response. Computed tomography revealed a 7 × 5 cm mass with indistinct borders and heterogeneous internal density extending from the cecum to the right lower abdominal wall. We diagnosed appendiceal abscess, however, percutaneous biopsy which was performed for differential diagnosis with appendiceal carcinoma showed no malignancy. Thereafter, the patient was followed up. Two months later, a blood test showed insignificant changes in the inflammatory response and a high serum carcinoembryonic antigen level (48.6 ng/mL). An ultrasound showed a mass contiguous to the appendix, extending to the abdominal wall, with abundant blood flow signals. Fluorodeoxyglucose-positron emission tomography showed a high accumulation of fluorodeoxyglucose in the mass. Four months after the initial visit, the patient had an open ileocecal resection combined with an abdominal wall resection based on the preoperative diagnosis of appendiceal carcinoma invading the abdominal wall. During laparotomy, an enlarged appendix tip extended from the internal inguinal ring outside the inferior epigastric artery to the abdominal wall. Histopathological examination of the appendiceal tumor revealed well-differentiated adenocarcinoma, T4b (abdominal wall), N0, Ly0, and V0. When a right lower abdominal mass extends from the cecum to the abdominal wall, appendiceal tumors associated with Amyand's hernia should be considered., Competing Interests: The authors have no competing interests to declare.

Appendiceal mucinous neoplasms are rare and can be associated with the development of disseminated peritoneal disease known as pseudomyxoma peritonei (PMP). Mucinous tumours identified on appendicectomy are therefore followed up to assess for recurrence and the development of PMP. In addition, individuals who initially present with PMP and are treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) are followed up to assess for recurrence. However, despite the concerted efforts of multiple expert groups, the optimal imaging follow-up protocol is yet to be established. The purpose of this article is to review the available evidence for imaging surveillance in these populations to identify the optimum post-resection imaging follow-up protocol., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Institute of Radiology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Serial fluorine 18 fluorodeoxyglucose ( 18 F-FDG) positron emission tomography-CT (PET/CT) is commonly used in human oncology to prognosticate and evaluate for therapeutic effectiveness. In this pilot study, dogs with naturally occurring appendicular osteosarcoma were evaluated with serial 18 F-FDG PET/CT in an attempt to assess for response to therapy, prognostic factors, and appropriateness of imaging intervals. Fourteen dogs were enrolled in the trial. All dogs had the initial 18 F-FDG PET/CT (PET1), with nine dogs having their end-of-therapy 18 F-FDG PET/CT (EoT PET) 3 months after stereotactic body radiation therapy (SBRT) to the primary tumor. The median percent change from the PET1 to the EoT PET for the standard uptake value maximum (SUV max% ) was -58% (range: -17 to -88%), metabolic tumor volume (MTV % ) was -99.8% (range: -65 to -100%), and total lesion glycolysis (TLG % ) was -99.8% (range: -75 to -100%), all of which were significant (P < .05, <.05, and <.05, respectively). On evaluation, it was found that volumes of GTV and CTV were significant for survival (P < .05 and <.05), MTV 1 , TLG 1 , and SUV max on the EoT PET (SUV maxEoT ) were predictive of metastasis (P < .05), and the SUV max% was significantly correlated to the time to first event (P < .05). Based on this data, serial 18 F-FDG PET/CT performed 3 months after SBRT can show a significant reduction in avidity, and the quantitative data collected may help predict metastatic disease in canine appendicular osteosarcoma., (© 2024 The Author(s). Veterinary Radiology & Ultrasound published by Wiley Periodicals LLC on behalf of American College of Veterinary Radiology.)

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., Competing Interests: The authors declare no conflict of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background: In the present study, we investigated the value of 18 F-fibroblast-activation protein inhibitor (FAPI) positron emission tomography/computed tomography ( 18 F-FAPI-42 PET/CT) to preoperative evaluations of appendiceal neoplasms and management for patients., Methods: This single-center retrospective clinical study, including 16 untreated and 6 treated patients, was performed from January 2022 to May 2023 at Southern Medical University Nanfang Hospital. Histopathologic examination and imaging follow-up served as the reference standard. 18 F-FAPI-42 PET/CT was compared to 18 F-fluorodeoxyglucose ( 18 F-FDG) PET/CT and contrast-enhanced CT (CE-CT) in terms of maximal standardized uptake value (SUVmax), diagnostic efficacy and impact on treatment decisions., Results: The accurate detection of primary tumors and peritoneal metastases were improved from 28.6% (4/14) and 50% (8/16) for CE-CT, and 43.8% (7/16) and 85.0% (17/20) for 18 F-FDG PET/CT, to 87.5% (14/16) and 100% (20/20) for 18 F-FAPI-42 PET/CT. Compared to 18 F-FDG PET/CT, 18 F-FAPI-42 PET/CT detected more regions infiltrated by peritoneal metastases (108 vs. 43), thus produced a higher peritoneal cancer index (PCI) score (median PCI: 12 vs. 5, P < 0.01). 18 F-FAPI-42 PET/CT changed the intended treatment plans in 35.7% (5/14) of patients compared to CE-CT and 25% (4/16) of patients compared to 18 F-FDG PET/CT but did not improve the management of patients with recurrent tumors., Conclusions: The present study revealed that 18 F-FAPI-42 PET/CT can supplement CE-CT and 18 F-FDG PET/CT to provide a more accurate detection of appendiceal neoplasms and improved treatment decision making for patients., (© 2024. The Author(s).)

Objective: To evaluate the association between clinical and imaging with surgical and pathological findings in patients with suspected neuroendocrine tumor of appendix and/or appendix endometriosis., Methods: Retrospective descriptive study conducted at the Teaching and Research Institute of Hospital Israelita Albert Einstein , in which medical records and databases of patients with suspected neuroendocrine tumor of appendix and/or endometriosis of appendix were analyzed by imaging., Results: Twenty-eight patients were included, all of which had some type of appendix alteration on the ultrasound examination. The pathological outcome of the appendix found 25 (89.3%) lesions compatible with endometriosis and three (10.7%) neuroendocrine tumors. The clinical findings of imaging and surgery were compared with the result of pathological anatomy by means of relative frequency., Conclusion: It was possible to observe a higher prevalence of appendix endometriosis when the patient presented more intense pain symptoms. The image observed on ultrasound obtained a high positive predictive value for appendicular endometriosis., Competing Interests: Conflicts to interest: none to declare., (© 2024. Federação Brasileira de Ginecologia e Obstetrícia. All rights reserved.)

Introduction: Mucocoele of the appendix occurs in 0.2-0.7% of people in the world without any well-defined clinical symptoms. It occurs when there is an accumulation of mucous in the lumen of the appendix., Case Presentation: We present three cases: a 48-year-old male admitted to the emergency room with a one-day history of right iliac fossa pain. Abdominal examination was suggestive of acute appendicitis. The initial abdominal computerised tomography scan was reported as being unremarkable. At surgery, a firm tumour of the appendix was found, and a limited right hemicolectomy was done. Histopathology confirmed a mucocoele of the appendix with borderline mucinous histology.The second case is a 63-year-old man who presented with a one-year history of abdominal distension and weight loss. Previous abdominal ultrasound was suggestive of liver cirrhosis with significant ascitic fluid. Abdominal magnetic resonance imaging found an appendix mucocoele with infiltration of the omentum and scalloping of the liver surface suggestive of pseudomyxoma peritonei. A percutaneous biopsy of the omental mass confirmed metastatic mucinous adenocarcinoma of the appendix.The third case is a 68-year-old man who, during an annual medical check-up, had an incidental finding of a cystic right iliac fossa mass on ultrasound, confirmed on abdominopelvic computerised tomography scan to be an appendix mucocele. He had laparoscopic appendicectomy. The histopathological diagnosis confirmed a mucinous cystadenoma of the appendix., Conclusion: Preoperative diagnosis of appendiceal mucocoele is difficult and commonly discovered intraoperatively. The prognosis is good for the histologically benign type, but it is poor when malignant or peritoneal lesions are present., Funding: None declared., Competing Interests: Conflict of interest: None declared, (Copyright © The Author(s).)

Appendiceal tumours encompass a wide spectrum of differential diagnoses and frequently present with clinical features of appendicitis. We report the case of a 43-year-old woman who presented with epigastric pain, dyspepsia and bloating. An atypical right para-iliac mass was detected on abdominal ultrasound, and computed tomography (CT) identified an appendiceal tumour. The tumour subtype remained indeterminate following Gallium-68 Dotatate positron emission tomography (PET); however, an appendiceal neuroendocrine tumour was suspected. Surgical resection with laparoscopic en bloc appendicectomy and limited caecectomy was performed, and histopathological assessment confirmed an appendiceal schwannoma. The report is followed by a review of the literature. To our knowledge, there have been fourteen reported cases of appendiceal schwannoma. The preoperative diagnosis can be challenging and appendiceal schwannoma had not been suspected in any of the reported cases, while a suspected diagnosis of neuroendocrine tumour or gastrointestinal stromal tumour was common. Definitive diagnosis requires immunohistochemical assessment and S100 is the hallmark. No personal or family history of underlying neurofibromatosis (NF) type 1 or type 2 has been reported to date. As for other gastrointestinal schwannomas, complete surgical resection is the recommended treatment for appendiceal schwannoma. Following this, despite lack of long-term follow-up, no cases of recurrence have been reported thus far., (© 2022. The Author(s), under exclusive licence to Royal Academy of Medicine in Ireland.)

Aim: To review the radiological terminology used to describe dilated mucin-containing appendiceal lesions with correlation to the histopathological diagnosis., Materials and Methods: Radiology and histopathology reports for all patients with an abnormally dilated appendix referred to a tertiary peritoneal malignancy centre, between January 2021 and December 2021, were reviewed., Results: Overall, 213 patients were included with a median appendiceal diameter of 25.5 mm (range 10-125 mm). Peritoneal disease was present in 109 patients, with the remaining 104 cases demonstrating a dilated appendix only. Local radiology reports were available for 201 cases with the appendix described in 168 cases as appendiceal mucocoele (n=104), appendiceal neoplasm (n=40), appendicitis (n=18), and dilated appendix (n=6). The appendix was not mentioned in 33/201 (15%), either misinterpreted as other pathology (n=15) or not reported (n=18). Peritoneal malignancy histopathology reports were available in 188 cases and reported as low-grade appendix mucinous neoplasm (LAMN, n=144), high-grade appendix mucinous neoplasm (HAMN, n=13), LAMN with foci of HAMN (n=2), LAMN with neuroendocrine tumour (n=2), LAMN with goblet cell adenocarcinoma (n=1), goblet cell adenocarcinoma (n=8), mucinous adenocarcinoma (n=14), non-mucinous adenocarcinoma (n=1), and benign histology (n=3). Only one case of a true inflammatory "mucocoele"/retention cyst was reported., Conclusion: In this cohort of patients, the overwhelming majority of dilated, mucin-filled appendices contained malignant cells and benign mucin-filled appendices were rare. The present authors advocate that the term "likely appendix mucinous neoplasm" should replace "appendix mucocoele" to represent the most likely pathology and facilitate less ambiguous interpretation in management decisions., (Copyright © 2022 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Competing Interests: Competing interests: None declared.

Competing Interests: The authors declare that they have no conflict of interest.

Background: Radiographically detected incidental appendiceal abnormalities, in this report termed "appendiceal incidentalomas" (AIs), are an ill-defined entity with an unknown prevalence of neoplasm. This study aimed to describe the prevalence, radiographic characteristics, and outcomes of patients with a diagnosis of AI., Methods: The study reviewed the electronic health records for patients at a single institution undergoing abdominopelvic computed tomography and magnetic resonance imaging (MRI) from 2000 to 2020 for non-appendix-related complaints with mention of appendix abnormality in the radiology report. The suggested diagnosis at the index imaging was recorded. Outcomes were compared between the operative and non-operative patients., Results: Of 5197 records, 484 were identified as reports of AIs (9 % of screened patients). Neoplasms were suggested radiographically in 16 % (n = 79) of the records, 59 % (47/79) of which were resected. Pathologically, 32 of the abnormalities were confirmed as neoplasms, yielding a diagnostic accuracy of 68 %. Compared with the non-operative patients, the operative patients had AIs with a larger mean diameter (22.7 ± 13.0 vs. 17.8 ±7.7 mm; p = 0.04), a higher colonoscopy rate (51 % vs. 22 %; p = 0.01), and diagnosis at a younger age (55.8 ± 15.6 vs. 67.2 ± 16.0 years; p = 0.003). The postoperative complications were minor (Clavien-Dindo grade 1 or 2) in 26 % and major (grades 3-5) in 4 % of the cases. During a median follow-up period of 28.3 months, 94 % of the patients were alive without disease, and 6 % died of other causes. The 32 non-operative suggested neoplastic AIs had a median follow-up period of 20.9 months. At this writing, 59 % of the operative patients are alive with a stable abnormal appendix, 13 % had no appendix abnormality at last follow-up visit, and 28 % have died of other causes., Conclusion: Neoplastic AIs are an uncommon finding and radiographically diagnosed with relatively high accuracy. Larger appendiceal diameter and younger age predict operative intervention. Although surgery is associated with favorable outcomes and minimal risk of postoperative complications, observation of suspected neoplastic AIs may be a safe alternative for select patients undergoing follow-up longitudinal imaging., (© 2022. Society of Surgical Oncology.)

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., Competing Interests: Conflict-of-interest statement: Authors declare no conflict of interests for this article., (©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.)

Mucin-producing neoplasms in the abdomen and pelvis are a distinct entity, separate from simple fluid-containing neoplasms and loculated fluid collections. Mucin is a thick gelatinous substance and-owing to its high water content-has imaging features that can be mistaken for those of simple fluid-containing neoplasms with multiple imaging modalities. However, mucin-producing neoplasms arise from specific organs in the abdomen and pelvis, with unique imaging appearances, knowledge of which is important to guide accurate diagnosis and management. With its large field of view and high soft-tissue resolution, MRI has advantages over other imaging modalities in characterizing these neoplasms. The authors focus on the spectrum of MRI features of such mucin-producing neoplasms and illustrate how-despite a varied organ origin-some of these neoplasms share similar MRI and histopathologic features, thereby helping narrow the differential diagnosis. One common finding in these tumors is that the presence of internal complexity and solid enhancing components increases as the degree of malignant transformation increases. Lack of internal complexity generally indicates benignity. These tumors have a varied range of prognosis; for example, a low-grade appendiceal mucinous neoplasm is indicative of a good prognosis, while a mucinous tumor of the rectum is known to manifest at an early age with aggressive behavior and poorer prognosis compared with its nonmucinous counterpart. Online supplemental material is available for this article. © RSNA, 2022.

Background: Cases with intussusception caused by either intestinal hemangiomas or appendiceal mucinous neoplasms are extremely rare., Case Presentation: In this study, we reported a 47-year-old male presented with paroxysmal abdominal pain and postprandial bloating for 3 days. CT results indicated a high possibility of secondary intussusception in ascending colon. Histopathology indicated a mixed type of cavernous and capillary hemangioma, combined with low-grade appendiceal mucinous neoplasms (LAMNs) and intestinal obstruction. The patient underwent laparotomy and right hemicolectomy. Finally, the patient was followed up for 4 months with no disease progression., Conclusions: Rare studies reported the intestine hemangiomas coincided with appendix low-grade mucinous tumor. Its manifestations are not specific, which is a challenge in the preoperative diagnosis. For cases with intussusception that was not observed in time, it may lead to intestinal necrosis and diffuse peritonitis. Additionally, the ruptured mucinous tumor in the appendix may lead to pathogenesis of pseudomyxoma peritonei. Therefore, accurate diagnosis and appropriate surgery-based treatment contribute to the improvement of prognosis and severe outcomes among these patients., (© 2022. The Author(s).)

Appendiceal tumours are uncommon neoplasms of the gastrointestinal tract. An understanding of the imaging appearances facilitates an accurate radiological description, which guides surgical and oncological management. In this study, a retrospective review of the CT imaging and histopathology of all cases of appendiceal tumours discussed at the oncology multidisciplinary meetings in a single centre, over an 8-year period (2012-2019) is performed. The array and incidence of both common and rare pathologies are investigated, and important characteristic imaging findings for radiologists to recognize are highlighted., (© 2021 The Authors. Journal of Medical Imaging and Radiation Oncology published by John Wiley & Sons Australia, Ltd on behalf of Royal Australian and New Zealand College of Radiologists.)

A 53-year-old lady presented with post-menopausal bleeding (spotting) for two days and abdominal pain for three months. CT scan revealed bilateral adnexal mass and ascites; and CEA and CA19.9 was raised. Histopathology of the resected tissues revealed mucinous carcinoma of bilateral ovaries and colon with omental metastasis. Generally, pseudomyxoma peritonei arises from primary ovarian or appendiceal adenomas or adenocarcinomas. Keywords: Adenocarcinomas; ascites; metastases; mucinous carcinoma; pseudomyxoma peritonei.

History A 57-year-old man with no remarkable past medical history presented to an outside institution with painless swelling in his right thigh of 6 months duration. He denied any trauma to the site. At that time, physical examination demonstrated swelling in his right upper thigh. All other work-up, including complete blood count and chest radiography, yielded negative results. The initial diagnosis was lymphangioma of the thigh. He continued to experience worsening swelling in his right upper thigh with no other symptoms over the next year. He was referred to our facility, where he underwent US evaluation of the thigh lesion, an MRI scan encompassing the entire extent of his thigh lesion, and a CT scan of his abdomen and pelvis.

Introduction: The aim of the current paper was to critically collect, select and summarize the evidence regarding diagnosis, treatment and follow up of primary tumors of the appendix., Methods: A literature review was performed by search and review of the scientific studies pertaining to the subject of our inquiry., Results: Recommendations regarding pimary tumors of the appendix were formulated on the basis of the collected evidence. CONCLUSION : Primary tumors of the appendix are rare and a high index of suspicion is required not to miss a potentially life threatening medical condition.

Acute appendicitis is the most common disease of the appendix. However, the differential diagnosis for an abnormal appendix includes other conditions that often present with symptoms and imaging features that overlap with acute appendicitis. In this pictorial essay, we review the normal anatomy of the appendix and outline the pathogenesis, clinical manifestations, and imaging findings that are characteristic of acute appendicitis and other less common appendiceal abnormalities. Inflammatory/non-neoplastic processes including appendiceal diverticulitis, stump appendicitis, foreign body appendicitis, Crohn's appendicitis, and appendiceal hernias are discussed. Neoplastic considerations include appendiceal neuroendocrine tumors, mucinous and non-mucinous (colonic type) epithelial neoplasms, and lymphoma. It is important for the radiologist to be able to differentiate these alternative diagnoses for the purpose of directing appropriate patient management.

Appendiceal mucocele is an obstructive dilatation of the appendix, which results from the filling of its lumen with mucus. This is a rare condition that is asymptomatic in half of the patients. Its severity depends on the cause of appendiceal dilatation. In a small percentage of cases, the dilated appendix ruptures, leading to the development of serious complication; this is termed as pseudomyxoma peritonei. Due to the possibility of malignant etiology of the mucocele, surgical resection remains an essential part of the treatment.

We describe a case of a mucosal prolapse syndrome (MPS)-like inflammatory polyp protruding from the appendiceal orifice, mimicking an appendiceal neoplasm. A 48-year-old man presented with lower abdominal pain and elevated white blood cell count and C-reactive protein level. Computed tomography showed a swollen appendix with multiple small saccular lesions and periappendiceal fat stranding and small saccular lesions in the ascending colon and cecum. Ultrasonography showed a swollen appendix 25 mm in diameter with multiple saccular structures and a periappendiceal high-echoic area, suggesting appendiceal diverticulitis. Colonoscopy revealed an erythematous lesion protruding from the appendiceal orifice. An ileocecal resection was performed based on a preoperative diagnosis of appendiceal diverticulitis and tumor. Histopathological examination of the appendix showed multiple mucosal herniations with infiltration of inflammatory cells, indicating appendiceal diverticulitis. The tumor was characterized by glandular duct hyperplasia and stromal expansion with smooth muscle hyperplasia and was diagnosed as an inflammatory polyp resembling an MPS lesion. Although several studies have shown the macroscopic and endoscopic appearance of MPS-like inflammatory lesions associated with colonic diverticular disease, this case was the first to present an inflammatory polyp associated with appendiceal diverticulitis in which the lesion protruding from the appendiceal orifice was masquerading as an appendiceal neoplasm.

Competing Interests: Competing interests: None declared.

Objective: To explore the clinicopathologic features and prognosis of female appendiceal mucinous tumor misdiagnosed as gynecological neoplasm. Methods: The clinical data of 12 cases of suspected gynecological neoplasm but confirmed as appendiceal mucinous tumor by operation and pathology in Beijing Obstetrics and Gynecology Hospital hospital from 2010 to 2019 were collected. The clinicopathologic features, treatment and prognosis of these patients were analyzed. Results: The median age of 12 patients was 58 years old and the clinical manifestations were atypical, including 5 cases with gastrointestinal symptoms, 6 cases with touched lesion in the right adnexal area, 3 cases with pseudomyxoma of peritonei, and 4 cases with increased serological tumor markers and ascites. Before operation, ultrasonic diagnosis showed cystic or cystic-solid mass in the right adnexal region in all cases. Pelvic and abdominal enhanced CT and/or enhanced MRI were performed in 5 cases. Two cases indicated possible origin of appendix and 1 case indicated lymphatic cystic tumor. Laparoscopic or laparotomy exploration was performed in all patients, during the operation 7 cases were performed appendectomy, 4 cases were performed tumor cell reduction and 1 case was treated in another hospital after laparotomy exploration. Eleven cases were diagnosed as low-grade appendiceal mucinous tumor and 1 case as appendiceal mucinous adenocarcinoma by postoperative pathology. Among the 11 patients with low-grade appendiceal mucinous tumor, 9 cases had no recurrence, 1 case lost follow-up, 1 case died of breast cancer and 1 case died 18 months after the operation. Conclusions: Gynecologists should improve their ability to differentiate appendiceal mucinous tumor from gynecological neoplasm. They can include ultrasonic diagnosis and CT scanning into their preoperative physical examination to improve their examination ability, and strive for specialist or surgical treatment to achieve the best result.

Objectives: To assess CT signs to discriminate an appendiceal tumor versus a non-tumoral appendix in an acute appendicitis context., Methods: A 10-year bicentric retrospective case-control study was performed in adults. Patients with a histopathological appendiceal tumor and appendicitis were paired for age and sex with patients with non-tumorous appendicitis (1/3 ratio, respectively). Two senior radiologists blindly analyzed numerous CT findings with final consensus to perform univariate and multivariate statistical analyses. A diagnostic CT scan score was calculated with a bootstrap internal validation. Reproducibility was assessed based on the kappa statistic., Results: A total of 208 patients (51 +/- 21 years; 114 males) were included (52 patients in the tumor group and 156 in the non-tumor group). In the multivariate analysis, an appendicolith and fat stranding were protective factors with OR = 0.2 (p = 0.01) and OR = 0.3 (p = 0.02), respectively, while mural calcifications (OR = 47, p = 0.0001), an appendix mass (OR = 7.1, p = 0.008), a focal asymmetric wall abnormality (OR = 4.9, p = 0, 001), or a ≥ 15 mm diameter (OR = 3.5, p = 0.009) were positive predictive factors of an underlying tumor. Using a ≥1 cut-off, our diagnostic score had an AUC = 0.87 (95 % CI, 0.82-0.93) and a positive likelihood ratio = 13.5 (95 % CI, 6.7-27.1)., Conclusion: We developed a reliable scoring system based on CT findings, which is highly predictive of an underlying appendiceal neoplasm in an appendicitis context using a ≥1 cut-off., (Copyright © 2021 Elsevier B.V. All rights reserved.)

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., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Peutz-Jeghers syndrome is an autosomal dominant disorder characterized by hamartomatous polyposis, pigmentation, and malignant tumors. We report a case of ileocecal carcinoma that was incidentally detected during follow-up for Peutz-Jeghers syndrome. A 39-year-old man with solitary Peutz-Jeghers syndrome had undergone three abdominal surgeries. He had been followed up via upper and lower gastrointestinal endoscopy and small intestinal endoscopy. In the endoscopic examination of the lower gastrointestinal tract, a 35 mm large, bumpy, elevated lesion was observed in the cecum. This lesion was not observed 9 months earlier during lower endoscopy. Biopsy of the specimen confirmed tubulovillous adenoma and carcinoma. This lesion was judged to be an indication for operation, and we performed ileocecectomy + D3 lymph node dissection. From the excised specimen, poorly differentiated carcinoma and adenoma components in contact with Peutz-Jeghers-type polyps in the appendix were recognized. A review of the computed tomography image obtained 2 years ago confirmed appendiceal swelling. We suspect that the ileocecal carcinoma in the appendix may have rapidly developed within the 9 months, and was incidentally detected on lower endoscopic examination during follow-up. For the prevention of appendicular tumorigenesis, prophylactic appendectomy may be considered in certain cases during follow-up for Peutz-Jeghers syndrome.

We are presenting a compelling case of a 61-year-old female with a history of appendiceal mucinous adenocarcinoma (AMA) with a new complaint of irritative lower urinary tract symptoms. Magnetic resonance imaging (MRI) showed a semi-circumferential, T2 hyperintense, rim enhancing, and lacking restricted diffusion lesion involving the urethra and infiltrating the right perineal and internal obturator muscles. The suspected differential diagnosis was urethral malignancy, based on her cancer history and MRI findings. After interdisciplinary consensus, the patient underwent excision of the lesion, and pathology was consistent with metastasis from the primary tumor. The urethra is a rare site of primary malignancy and metastatic disease. In particular, a non-contiguous metastatic disease involving the urethra is exceedingly rare. To the best of our knowledge, this is the first report of an AMA metastasizing to the urethra., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: The incidence of underlying malignancy in appendicitis ranges between 0.5% and 1.7%. We sought to identify the subset of patients with appendicitis who are at increased risk of appendiceal malignancy., Methods: Using the Eastern Association for the Surgery of Trauma Multicenter Study of the Treatment of Appendicitis in America: Acute, Perforated, and Gangrenous database, we included all patients from 28 centers undergoing immediate, delayed, or interval appendectomy between 2017 and 2018. Univariate then multivariable analyses were performed to compare patients with and without malignancy and to identify independent demographic, clinical, laboratory, and/or radiological predictors of malignancy. Akaike information criteria for regression models were used to evaluate goodness of fit., Results: A total of 3,293 patients were included. The median age was 38 (27-53) years, and 46.5% were female patients. On pathology, 48 (1.5%) had an underlying malignancy (adenocarcinoma [60.4%], neuroendocrine [37.5%], and lymphoma [2.1%]). Patients with malignancy were older (56 [34.5-67] vs 37 [27-52] years, P < .001), had longer duration of symptoms before presentation (36-41 vs 18-23 hours, P = .03), and were more likely to have a phlegmon on imaging (6.3% vs 1.3%, P = .03). Multivariable analyses showed that an enlarged appendiceal diameter was independently associated with malignancy (odds ratio = 1.06, 95% confidence interval = 1.01-1.12; P = .01). The incidence of malignancy in patients >40 years with an appendiceal diameter >10 mm on computed tomography was 2.95% compared with 0.97% in patients ≤40 years old with appendiceal diameter ≤10 mm. The corresponding risk ratio for that population was 3.03 (95% confidence interval: 1.24-7.42; P = .02)., Conclusion: The combination of age >40 and an appendiceal diameter >10 mm is associated with a greater than 3-fold increased risk of malignancy in patients presenting with appendicitis., (Copyright © 2020 Elsevier Inc. All rights reserved.)

BACKGROUND Completely isolated enteric duplication cysts (CIDCs) are rare malformations that can occur at any site in the gastrointestinal system. This report describes a woman with a CIDC and an incidental appendiceal neuroendocrine tumor (ANET). CASE REPORT A 26-year-old woman who presented with dysmenorrhea was assessed by ultrasound (US), which revealed a pelvic mass. Other imaging modalities, including magnetic resonance imaging (MRI), failed to clarify the origin of the mass. Intraoperative findings during diagnostic laparoscopy revealed an isolated, ovaloid mass with autonomous peristalsis and a short pedicle towards the root of the ileal mesentery. In addition, the appendix appeared enlarged with a hardened consistency. The mass was resected and an appendectomy performed laparoscopically. The pelvic mass was diagnosed as a CIDC and the appendix was incidentally found to contain a pT3Nx carcinoid tumor. Based on histological examination and guidelines of the European Neuroendocrine Tumor Network (ENET), the patient later underwent a laparoscopic right hemicolectomy. CONCLUSIONS CIDC in adulthood is very rare, especially when combined with an incidentally discovered pT3Nx appendiceal carcinoid tumor. Neither US nor MRI was able to provide a precise preoperative diagnosis. Diagnostic laparoscopy clarified the nature of the mass and revealed a lesion missed during the preoperative workup. Because of the diagnosis of ANET, the patient subsequently underwent a laparoscopic right hemicolectomy.

Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht.