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.
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