IntroductionScientific literature regarding the characterization of lymphocyte subpopulations of the cecal appendix is sparse, with few precedents limited to immunohistochemical techniques.MethodsWe conducted a prospective pilot study to characterize lymphocyte subpopulations of the cecal appendix in children. Participants were divided into three groups: (1) patients without histological acute appendiceal inflammation, (2) patients with histological uncomplicated acute appendicitis, and (3) patients with histological complicated acute appendicitis (gangrenous, perforated). A fresh sample of the base of the appendix was taken from all patients and a flow cytometric study was performed. Quantitative variables were compared using Kruskal-Wallis test and Mann-Whitney U test.ResultsThis study included 57 patients divided into Group 1 (n = 5), Group 2 (n = 37), and Group 3 (n = 15). Median values (IQR) of the percentage of B-lymphocytes were 67.8 [66.8-68.1] in group 1, 61.15 [53.74-66.4] in group 2, and 52.1 [33-62.02] in group 3 (p = 0.02). Median values (IQR) of the percentage of NK-lymphocytes were 0.26 [0.2-0.3] in group 1, 0.55 [0.37-0.66] in group 2, and 0.84 [0.35-1.45] in group 3 (p = 0.008). Median values (IQR) of the percentage of T-lymphocytes were 31.9 [31.7-33.1] in group 1, 37.68 [32.15-45.69] in group 2, and 46.9 [37.03-67] in group 3 (p = 0.02). Pair comparisons of groups 2 and 3 also showed significant differences in the percentage of B lymphocytes (p = 0.03) and NK-lymphocytes (p = 0.02).ConclusionsSignificant differences in lymphocyte subpopulations were identified according to the histologic grade of the cecal appendix. More specifically, a lower percentage of B-lymphocytes and a higher percentage of T- and NK-lymphocytes were observed in cases of acute appendicitis. These findings must be confirmed and their etiopathogenic, diagnostic, and prognostic implications elucidated in future studies with larger sample sizes.