Ampullary tumors exhibit increased Fusobacterium in both the tumor surface and surrounding duodenal mucosa during carcinoma progression

Understanding the complex interplay between intestinal microbiomes and ampullary tumors is crucial for distinguishing between adenomas and carcinomas, especially when considering the role of Fusobacterium. We characterized the microbiome associated with ampullary tumors using samples collected from the tumor surface (tumor samples, TSs) and surrounding normal duodenal mucosa (normal samples, NSs) via brush rubbing. In total, samples from 17 patients, divided into an adenoma group (n = 11) and a carcinoma group (n = 6), were analyzed. The Shannon α-diversity index was significantly higher in the carcinoma group compared with the adenoma group, indicating a more diverse bacterial community in the carcinoma environment. The TSs of the carcinoma group exhibited enrichment of Fusobacterium, Leptotrichia, Methylorubrum, and Micrococcus. The relative abundance of Fusobacterium increased as the tumor progressed. The NSs of the carcinoma group showed a higher presence of Fusobacterium, Porphyromonas, Granulicatella, Rikenellaceae RC9 gut group, and Solobacterium, whereas Bergeyella was more prevalent in the adenoma group. These results suggest that ampullary carcinomas exhibit a characteristic microbiome compared to adenomas. Fusobacterium is enriched in the tumor and surrounding normal duodenal mucosa, increases in abundance as the tumor progresses, and may be associated with ampullary tumors.