The role of Veillonella species in oral carcinogenesis: is prevalence linked to oral squamous cell carcinoma?

Oral squamous cell carcinoma (OSCC) remains a significant health challenge because of its aggressive nature and poor survival outcomes. While established risk factors such as tobacco use, alcohol consumption, and human papillomavirus play critical roles, increasing evidence suggests that oral microbial dysbiosis may contribute to carcinogenesis. Among oral commensals, Veillonella species have gained attention because of their ecological role in oral biofilms and metabolic interactions with other microbes, and have also been increasingly identified in altered abundances within OSCC patient samples. This narrative review synthesizes available clinical, epidemiological, and molecular studies investigating the prevalence and biological roles of Veillonella species in OSCC. Relevant English-language publications between 2000 and 2025 were identified through database searches in Pubmed Scopus and Web of Science using keywords related to Veillonella, oral microbiome, dysbiosis, and OSCC. The reviewed evidence reveals a dynamic and stage-dependent shift in Veillonella abundance during oral carcinogenesis. Several studies report enrichment of Veillonella in oral potentially malignant disorders and early tumorigenesis, whereas reduced levels are frequently observed in advanced OSCC. These findings suggest that Veillonella may function as an ecological modulator of tumor-associated microbiota rather than as a single pathogenic driver. Proposed mechanisms include metabolic cross-feeding with lactic-acid-producing bacteria, modulation of inflammatory pathways, biofilm restructuring, and host-microbe metabolic signaling. Overall, current evidence supports a microbial ecological shift model, in which Veillonella participates in early dysbiotic transitions preceding OSCC development but may decline as tumor microenvironments evolve. Further standardized and multiomics studies are needed to clarify its potential as a microbiome-based biomarker and therapeutic target.