Incidental appendiceal neoplasms in a multicenter registry of appendicitis management

Nonoperative management of uncomplicated appendicitis has become increasingly common, raising concerns that occult appendiceal neoplasms may remain in situ. We sought to characterize the incidence, histologic subtypes, and risk factors of incidental appendiceal neoplasms.

This retrospective cohort study included randomly selected adult patients presenting with an initial episode of acute appendicitis at 6 US hospitals from 2012-2014 and 2018-2021. Exclusion criteria included preoperatively suspected appendiceal mass. Patients were followed for 6 months from initial presentation. The primary outcome was the presence of an incidental primary appendiceal neoplasm on appendectomy. Patient characteristics were compared between those with and without neoplasms.

Inclusion criteria were met by 1,822 patients. Incidental neoplasms were identified in 24 (1.3% [95% CI, 0.9%-2.0%]) patients. These patients were older (49 years versus 34 years, P = .006) but otherwise similar by demographics and clinical severity; complicated disease was found in 20.8% of patients with neoplasms versus 19.8% of patients without neoplasms (P = 1.000) on appendectomy. Rate of incidental neoplasms was 0.6% (0.3%-1.3%) among patients 18-39 years of age, 2.0% (1.1%-3.6%) in patients 40-69 years of age, and 4.8% (1.7%-11.4%) in patients 70 years of age or older. Neuroendocrine tumors were most common at 33.3% (8/24), followed by low-grade appendiceal mucinous neoplasms (6/24), sessile serrated adenomas (6/24), goblet cell adenocarcinomas (3/24), and gastrointestinal stromal tumor (1/24).

Incidental neoplasms were associated with increased age but not clinical severity of appendicitis, though masses suspected on preoperative imaging were excluded. Nonoperative management may be offered to select patients. However, neoplasm risk should be included in shared decision making in all patients, and follow-up testing should be considered for patients older than 40.