Introduction
There are very few large data studies on appendiceal neoplasm incidence in appendicitis patients, especially ones that differentiate between complicated appendicitis (CA) and uncomplicated appendicitis (UA), and between different age groups. We sought to compare the incidence of appendiceal neoplasms in patients with CA versus UA, further stratified by decades of life, using a large patient database.

Methods
This was a retrospective cohort study utilizing the ACS-NSQIP database in the years 2016 to 2020. All patients undergoing an appendectomy with no previous abdominal operations were eligible for inclusion. CA was defined as having operative findings of perforation and/or abscess. UA was defined as having no operative findings of perforation or abscess. Age was analyzed both as a continuous variable and as a categorical variable separated into different decades (< 21, 21-30, 31-40, 41-50, 51-60, 61-70, 71-80, and > 80).

The primary outcome assessed was appendiceal neoplasm incidence. A univariable and multivariable logistic regression model was built to evaluate the association between neoplasm incidence as the outcome variable and CA vs. UA as the main independent variable, further stratified by age. The model was adjusted for any confounding variables.

Results
A total of 60,785 patients were included with a mean age (SD) of 40 (± 16.4) years and a sex distribution of 49.7% female. 14,321 CA and 46,464 UA cases were compared. Their mean ages (SD) were 47 (± 17.4) and 38 (± 15.5) years, respectively (P < 0.001). There was a significant difference in overall appendiceal neoplasm incidence in patients with CA vs. UA (1.2% vs. 1.7%, respectively, P < 0.001). When further stratified by age as a categorical variable, the difference in neoplasm incidence between CA and UA became more significant with rising age (Table 1).

In patients with UA, a significant increase in neoplasm incidence was observed in patients older than 50 years compared to the overall incidence of 1.7% in the total population (P < 0.00001, Table 1). In patients with CA, a significant increase in neoplasm incidence was observed in patients older than 70 years compared to the overall incidence of 1.2% in the total population (P < 0.00001, Table 1).

In multivariable logistic regression with backward elimination, the odds of appendiceal neoplasm incidence in UA were two times more than that in CA.

Conclusion
UA has a higher rate of appendiceal neoplasm incidence compared to CA. This difference becomes more prominent as the patient ages. This data is supportive of surgical management of appendicitis, especially in patients older than 50.