Histopathological study of the localization/distribution of Fusobacterium nucleatum in esophageal cancer

Fusobacterium nucleatum is implicated in esophageal cancer; however, its distribution in esophageal cancer tissues remains unknown. This study aimed to clarify the presence and distribution of F. nucleatum in esophageal cancer tissues using fluorescence in situ hybridization (FISH). Tissues collected from 70 patients with esophageal squamous cell carcinoma were examined using FISH. Corresponding normal epithelium and metastatic lymph nodes were assessed. F. nucleatum was identified more frequently in esophageal cancer tissues than in the normal epithelium. F. nucleatum also showed significant correlation with factors associated with tumor progression, such as pT factor and tumor size. As tumor progression advanced, the area occupied by F. nucleatum gradually became larger. F. nucleatum positivity was observed around the deep edge of the tumor nest (border-dense type) or identified diffusely in the tumor nest (diffuse distributed type). Furthermore, F. nucleatum was observed in metastatic lymph nodes, lesions of venous invasion, and walls of veins in normal epithelium. In conclusion, we visualized F. nucleatum using FISH and identified different distribution patterns of F. nucleatum, highlighting the spot density of its presence in tumor tissues. Recognizing this quantitative change is pivotal for establishing F. nucleatum as a reliable biomarker.