Figure 2.

Oral carcinogenesis. Normal oral mucosa is a stratified layer of epithelial cells arranged over a basement membrane that separates epithelial cells from connective tissue and blood vessels. When oral mucosa is challenged with external stressors, such as tobacco, alcohol or human papilloma virus (HPV) infection, cells in the deepest layers undergo morphological alterations in shape and size. This novel state represents an adaptation response against a harmful stimulation, which is known as oral dysplasia. Oral dysplasia might be categorized as mild, moderate or severe, according with the extension of the lesion and the presence of molecular markers induced as result of the altered genetic expression. Oral dysplasia is considered the previous stage before oral squamous cell carcinoma (OSCC) and the strongest predictor of malignant transformation to cancer. During OSCC, massive phenotypic changes affect all epithelial layers, and it is extended over the tissue border, with ruptures of the basement membrane, in a process that allows the invasion of the connective tissue and incorporation into blood vessels (intravasation).