Oncologic Risk of Missed Appendiceal Tumors in Acute Appendicitis

Importance: Antibiotic-only management (AOM) for uncomplicated acute appendicitis is increasingly adopted, raising concern about missed appendiceal neoplasms. Objective: To assess the prevalence, histologic spectrum, and predictors of incidental appendiceal tumors after appendectomy for acute appendicitis. Design, Setting, and Participants: This single-center retrospective cohort study was conducted from January 1, 2013, to December 31, 2021, at the tertiary surgical emergency center at Saint-Antoine Hospital in Paris, France. All consecutive adult patients undergoing appendectomy for acute appendicitis were eligible for inclusion. Data were analyzed in June 2025. Exposure: Standard surgical management with appendectomy (no AOM); preoperative clinical variables, laboratory values, and imaging findings were assessed as potential predictors of appendiceal tumors. Main Outcome and Measures: Prevalence and histopathological classification of incidental appendiceal neoplasms identified after appendectomy for acute appendicitis and preoperative clinical and radiologic factors associated with aggressive tumors. Results: Among the cohort, median (IQR) age was 32 years (25-43), and 999 patients (44%) were female. Among 2293 appendectomies, 37 (1.6%) had malignant or premalignant lesions and 8 (0.3%) had benign nondysplastic lesions. Neuroendocrine tumors (NETs) (n = 22) predominated; all were grade 1 (G1) and smaller than 2 cm, with 19 (86%) measuring 1 cm or less without recurrence after 34 months of follow-up. Other lesions included low-grade appendiceal mucinous neoplasms (n = 5), metastatic tumors (n = 3), goblet cell carcinomas (n = 2), mucinous adenocarcinoma (n = 1), and low-grade dysplastic polyps (n = 4). Compared with nonneoplastic appendicitis, aggressive tumors (putting aside G1 NETs