The Role of Oral Yeasts in the Development and Progression of Oral Squamous Cell Carcinoma: A Scoping Review

The role of oral yeasts in oral squamous cell carcinoma (OSCC) has gained attention due to evidence linking fungal dysbiosis to carcinogenesis. While Candida albicans has been the primary focus, emerging studies highlight the importance of non-Candida species yeast genera. This scoping review synthesises the evidence on the role of oral yeasts, including Candida spp. and non-Candida species, in the development and progression of OSCC. A PRISMA-ScR-guided search was conducted in Medline, Embase, EBM Reviews, and CINAHL. Observational and experimental studies involving humans with OSCC, oral potentially malignant disorders (OPMDs), or oral epithelial dysplasia (OED) were included. This review analysed 75 studies. Research on oral yeast in OSCC has progressed since the 1970s, with advancements in identification techniques-from conventional culture methods to metagenomic sequencing and multi-omics approaches-alongside improved animal and cellular models of OSCC. These methodological advancements have identified notable distinctions in the oral mycobiome between carcinomatous and healthy states. Clinical findings reinforce the hypothesis that oral yeasts, particularly Candida spp., actively contribute to the dysplasia-carcinoma sequence. Emerging evidence suggests that oral yeasts may significantly modulate events contributing to OSCC progression. However, further mechanistic studies and robust clinical evidence are essential to establish causality and clarify their role in OSCC.