Magnifying Narrow-Band Imaging with Acetic Acid Spray for Superficial Non-Ampullary Duodenal Epithelial Tumors Based on the Mucin Phenotype

<b><i>Introduction:</i></b> This study aimed to identify the characteristics of superficial non-ampullary duodenal epithelial tumors (SNADETs) based on the mucin phenotype using magnifying narrow-band imaging with acetic acid spray (MA-NBI) and evaluate the efficacy of MA-NBI in differentiating gastric-type (G-type) from intestinal-type (I-type) lesions. <b><i>Methods:</i></b> We retrospectively identified 59 resected SNADETs in 59 patients who underwent MA-NBI. We evaluated surface patterns using MA-NBI to differentiate G-type from I-type lesions. Surface structures were classified into three patterns: tubular, villous, or oval structures. Lesions displaying a single pattern among the three patterns were classified as monotype, whereas those displaying multiple surface patterns were classified as mixed type. In addition, lesions with disorganized and unclear structures with irregular margins were classified as irregular surface structures. <b><i>Results:</i></b> In total, 32 (54%), 26 (44%), and 1 (2%) lesions were classified as Vienna category 3, 4, and 5 tumors, respectively, whereas 49 (83%) and 10 (17%) were classified as I- and G-type lesions, respectively. Oval structures were more frequently observed in G-type lesions (70%), whereas tubular structures were more frequently observed in I-type lesions (78%) (<i>p</i> &#x3c; 0.001). Category 4 and 5 lesions had significantly higher mixed and irregular surface structure rates than category 3 lesions (41 vs. 6%, <i>p</i> = 0.003 and 81 vs. 3%, <i>p</i> &#x3c; 0.001, respectively). <b><i>Conclusion:</i></b> MA-NBI can distinguish the mucin phenotypes of SNADETs and may facilitate histological grade diagnosis.