Introduction
Studies evaluating rate and histology of appendiceal neoplasms between complicated and uncomplicated appendicitis include small number of patients. Therefore, we sought to perform a meta-analysis and systematic review comparing the rates and types of appendiceal neoplasm between complicated and uncomplicated appendicitis.

Methods
We included articles published from the time of inception of the datasets to September 30, 2022. The electronic databases included English publications in Ovid MEDLINE In-Process & Other Non-Indexed Citations, Ovid MEDLINE, Ovid EMBASE, and Scopus.

Results
A total of 5313 patients with appendicitis enrolled in 7 comparative studies were included. The overall mean age was 52.4 years (SD 23-89), and there was a male predominance (87%). Based on intra-operative findings, 1943 (38%) had complicated appendicitis and 3175 (62%) had uncomplicated appendicitis. Overall incidence rate of neoplasm was 2.54%. No significant difference was found in incidence rate of appendiceal neoplasm between complicated (3.98%) and uncomplicated (1.57%) appendicitis (OR 0.49, 95% CI 0.18- 1.33). Most common overall appendiceal neoplasms were: Neuroendocrine Tumors (NET) (53.0%), Nonmucinous Adenocarcinoma (27.4%), Mixed Adeno-Neuroendocrine Tumor (MANEC) (12.5%), Mucinous Adenocarcinoma (6.7%), and Adenoma (0.35%). There was a significant difference between complicated and uncomplicated appendicitis in rates of adenocarcinoma (50% vs 13%), NET (31% vs 74%), and MANEC (19% vs 13%) (P<0.001).

Conclusion
While there was no significant difference in overall rate of neoplasm between complicated and uncomplicated appendicitis, NET rate was significantly higher in uncomplicated appendicitis while Adenocarcinoma rate was significantly higher in complicated appendicitis.