The clinicopathological features of submucosal invasive non-ampullary duodenal carcinoma

Abstract Background Little is known about submucosal invasive non-ampullary duodenal carcinoma because of its extreme rarity, so we investigated the clinicopathological features, comparing submucosal invasive carcinoma (SM-Ca) with mucosal carcinoma (M-Ca) and advanced carcinoma (Ad-Ca). Methods We retrospectively analyzed 165 sporadic non-ampullary duodenal carcinomas (SNADCs) at 4 institutions between January 2003 and December 2018. In addition, we compared the mucin phenotype between SM-Ca and M-Ca. Results There were only 11 cases (7%) of SM-Ca, while there were 70 cases of M-Ca (42%) and 84 cases of Ad-Ca (51%). Although the distribution of M-Ca was almost equal between the oral and anal sides of the papilla of Vater, all SM-Ca was located on the oral-Vater (P = 0.013) and Ad-Ca tended to be located on the oral-Vater (P = 0.020). Mixed macroscopic type was more frequent in SM-Ca than in M-Ca (64% vs. 10%, P < 0.001). There was no significant difference in tumor diameter between M-Ca and SM-Ca, but 45% of SM-Ca were ≤ 10 mm. 73% (8/11) of SM-Ca were classified as gastric phenotype and no lesions were intestinal phenotype, whereas most M-Ca were intestinal phenotype (67%, 8/12). Conclusions SM-Ca was highly associated with tumor location (oral-Vater) and gastric mucin phenotype, different from M-Ca. The possibility of SM-Ca should be considered when superficial SNADCs are located on oral-Vater and have mixed macroscopic type even if tumor diameters are ≤ 10 mm.