The risk of neoplasms in appendiceal abscess: what emergency surgeons should know.

Introduction: A subset of patients with acute appendicitis presents with complicated disease characterized by periappendiceal abscess. Although appendiceal neoplasms are rare in uncomplicated appendicitis, recent evidence suggests a higher incidence in patients with appendicitis complicated by abscess, particularly in older adults. Because preoperative imaging has limited accuracy for tumor detection, the optimal management strategy remains debated. This narrative review summarizes current evidence on the incidence, histology, diagnostic limitations, and management implications of appendiceal neoplasms in patients with appendiceal abscess. Methods: A literature search was conducted in MEDLINE (PubMed) and the Cochrane Central Register of Controlled Trials from inception to November 2025. Eligible studies included randomized controlled trials, prospective and retrospective cohort studies, and case-control studies addressing complicated acute appendicitis with periappendiceal abscess and the incidence or characteristics of appendiceal neoplasms. Data were synthesized qualitatively through a narrative approach. Results: Primary studies show a low incidence of appendiceal neoplasms in uncomplicated acute appendicitis, generally below 2%. Patients with appendicitis complicated by periappendiceal abscess demonstrate substantially higher neoplasm rates, reaching 10-15% in population-based cohorts and selected interval appendectomy series. Most tumors are diagnosed incidentally on postoperative histopathology. Neuroendocrine tumors are more frequently identified in patients with uncomplicated acute appendicitis, whereas low-grade appendiceal mucinous neoplasms predominate in cases complicated by periappendiceal abscess. Invasive adenocarcinoma is also reported across both clinical presentations, with a higher prevalence in older patients. Age is the strongest predictor of underlying neoplasia, with a marked risk increase above 35-40 years. Pediatric studies consistently show a negligible risk of malignancy, with rare incidental neuroendocrine tumors and no association between appendiceal abscess and epithelial cancer. Conclusions: Appendiceal abscess in adults aged 35 years or older is associated with a clinically relevant risk of underlying neoplasia that cannot be reliably excluded preoperatively. Interval appendectomy after successful non-operative management provides diagnostic certainty and oncologic safety in this population. Standardized imaging-based definitions and international registries focused on CT-confirmed appendiceal abscess are needed to refine incidence estimates and optimize management strategies.