Oral squamous cell carcinoma is a malignant neoplasm that arises from the oral mucosa. Microscopically it can appear as well-differentiated, moderately differentiated, or poorly differentiated. This is termed “grade” and is somewhat subjective and loosely related to prognosis. In contrast, stage of disease, which takes into consideration the size of the tumor, the nodal involvement and whether metastasis has occurred, is more objective and is more closely related to prognosis.
Despite the level of differentiation, squamous cell carcinoma demonstrates invasion of the underlying tissues by groups of malignant epithelial cells. Invasion may penetrate lymphatic and blood vessels, accounting for routes of metastatic spread. Neural invasion, accounts for pain, usually only felt in advanced disease.