Association of mucin phenotypes, macroscopic type, and location with invasion depth in early nonampullary duodenal carcinomas

To investigate retrospectively the clinicopathological features of nonampullary duodenal intramucosal carcinoma (M-Ca) and submucosal carcinoma (SM-Ca). Seventy-three patients (67 with M-Ca and seven with SM-Ca) were included. The assessed clinical variables included patient age, sex, treatment procedure, lesion location, color, and macroscopic type. Pathological outcomes included invasion depth, predominant histological type, lymphovascular invasion, and mucin phenotype. SM-Ca lesions were predominantly located in the duodenal bulb (28.6%) or the oral side of the major papilla in the second portion (57.1%), while M-Ca lesions were primarily located in the second portion (97.0%) (<i>p</i> = 0.029). The superficially elevated type was predominant in the M-Ca group (43.3%), while the protruded type was predominant in the SM-Ca group (42.9%) (<i>p</i> = 0.034). A submucosal tumor-like appearance was more prevalent in the SM-Ca group (28.6%) than in the M-Ca group (1.5%) (<i>p</i> = 0.022). Well-differentiated adenocarcinomas were predominant in both groups (M-Ca, 97%; SM-Ca, 71.4%), with moderately differentiated and papillary adenocarcinomas being more prevalent in the SM-Ca group (14.3% each) (<i>p</i> = 0.042). The gastric mucin phenotype was significantly more prevalent in the SM-Ca group (71.4%) than in the M-Ca group (2.6%) (<i>p</i> &lt; 0.0001). The median depth of submucosal invasion was 1,200 µm in the SM-Ca group. No lymph node metastasis or recurrence was observed. Nonampullary duodenal submucosal carcinomas are characterized by their location on the oral side of the major papilla, protruded macroscopic type, and gastric mucin phenotype. These findings offer insights into distinguishing M-Ca from SM-Ca.