Variations in Epithelial Lining of Duplication Cysts Cannot be Explained by Known Theories

<i>Objectives.</i> Duplication cysts are found in any part of the gastrointestinal tract from the oropharynx to anus. Although duplication cysts usually have similar epithelium with the adjacent organ, respiratory epithelium in the enteric duplication cysts is rarely reported. This study was performed to evaluate the variations in the epithelial lining of duplication cysts and its clinical implications. <i>Methods.</i> Patients diagnosed with duplication cysts between 2012 and 2022 were retrospectively reviewed to assess their histopathological results, clinical aspects, treatment options, and demographic characteristics. <i>Results.</i> Twenty-five patients were included. The mean age was 4 years, male-to-female ratio was 15:10. The localizations of duplication cysts were ileum (n = 12), duodenum(n = 4), stomach(n = 3), jejunum(n = 2), colon(n = 2), thoracoabdominal(n = 2), and rectum(n = 1). Most common presentation was abdominal pain (36%). Intestinal (48%) and gastric (40%) epithelia were the most common finding. Four patients (16%) had respiratory epithelium: two in foregut duplication cysts, one each in ileal, and rectal duplications. Twenty-four percentage of patients had associated anomalies. Surgical interventions were performed on 22 patients. <i>Conclusion.</i> Duplication cysts show a wide range of epithelial linings. Respiratory epithelium can be found in not only foregut duplication cysts but also midgut and hindgut duplication cysts. Although the presence of respiratory epithelium did not have any impact on clinical findings, none of the previous theories explain the presence of respiratory epithelium different from foregut duplications.