Sporadic nonampullary duodenal adenoma/carcinoma is associated with not only colon adenoma/carcinoma but also gastric cancer: association of location of duodenal lesions with comorbid diseases.

It is well known that in patients with sporadic nonampullary duodenal adenoma/carcinoma (SNADA) with no polyposis syndrome, including familial adenomataous polyposis, the rates of colorectal adenoma/carcinoma are high. However, the prevalence rates of other tumor types, for example, gastric cancer, in SNADA patients remain unknown. In this study, we aimed to analyze the prevalence rate of comorbid diseases in SNADA patients. We retrospectively analyzed 78 patients with SNADA treated by endoscopic resection between May 2005 and September 2014 at our institution. Overall, 51 of the 78 (65.4%) SNADA patients had comorbid colorectal adenoma/carcinoma. Further, 10 of the 78 (12.8%) SNADA patients had comorbid gastric cancer, and all of them were positive for Helicobacter pylori infection. SNADA lesions were located significantly more frequently at the oral side of the major papilla in patients with H. pylori infection than in those without H. pylori infection (27 of 36 [75.0%] vs. 19 of 42 [45.2%], p = 0.008, chi-square test). In contrast, SNADA lesions were located significantly more frequently at the anal side of the major papilla in patients with colorectal adenoma/carcinoma than in those without colorectal adenoma/carcinoma (27 of 51 [52.9%] vs. 5 of 27 [18.5%], p = 0.003, chi-square test). SNADA patients showed comorbidity with not only colorectal adenoma/carcinoma but also gastric cancer. H. pylori infection is known to cause gastric cancer and may influence tumorigenesis of SNADA lesions at the oral side of the major papilla.