Supplementary Material for: Clinicopathological and Endoscopic Features of Non-Ampullary Duodenal Epithelial Tumors with Gastrointestinal Mixed Phenotype

Introduction: Non-ampullary duodenal epithelial tumors with a gastrointestinal mixed phenotype (mixed-type NADETs) have not been thoroughly analyzed. We aimed to elucidate the clinicopathological and endoscopic characteristics of mixed-type NADETs. Methods: A total of 229 NADETs from 218 patients collected from February 2010 to December 2023 were analyzed. Based on immunohistochemistry for MUC5AC, MUC6, MUC2, and CD10, the NADETs were classified into gastric phenotype (GP), gastric predominant mixed phenotype (GPP), intestinal predominant mixed phenotype (IPP), and intestinal type (IP). Results: Among the 229 NADETs, there were 20, 22, 69, and 118 lesions classified as GP, GPP, IPP, and IP, respectively. Tumor location (first/second/third) was GP=13/7/0, GPP=12/8/2, IPP=13/52/4, and IP=16/94/8 (P<0.01). Mean tumor sizes of GP, GPP, IPP, and IP were 14.7/18.5/10.9/10.3 mm (P<0.01), respectively. The ratio of category 4/5 by Vienna classification was 50.0, 68.2, 13.0, and 2.5% (P<0.01), respectively. In the comparisons between GP vs. GPP, and IP vs. IPP, white opaque substance was significantly less frequently observed in GP than in GPP (P<0.05), the ratio of category 4/ 5 was significantly higher in IPP than in IP (P<0.01), but no significant differences were observed in tumor location, coloration, macroscopic type, and endoscopic findings including magnifying endoscopy with narrow-band imaging. Conclusion: Mixed-type NADETs (GPP and IPP) exhibited similar endoscopic and clinicopathological characteristics to their predominant phenotypes, and may have a higher malignant potential than the pure phenotypes.