Considering the World Health Organization’s classification of Helicobacter pylori as a definite (class Ⅰ) carcinogen, the relationship between oral microbial community and tumors is gaining increased interest. This review focused on three relationships between oral microbiota and tumors, i.e., between oral Helicobacter pylori infection and gastric tumors, between oral microbiota and oral squamous cell carcinoma, and between human immunodeficiency virus and tumors. The aims were to realize the early diagnosis of tumors with oral microbiota and support studies on treatment development.
