The most common cancers in oral cavity are squamous cell carcinoma (OSSC), which accounts for more than 90% in oral cancers. The 5-year overall survival rate of early stage of OSCC is over 90%, while that of advanced stages is still poor. It is important to treat precancerous lesions including leukoplakia and erythroplakia to improve the prognosis. Malignant transformation rates of leukoplakia and erythroplakia range from 5% to 10% and 40% to 50%, respectively. Biopsy is performed to microscopically divide these lesions into oral intraepithelial neoplasia (OIN) /CIS and oral epithelial dysplasia. In addition to histological findings, immunohistochemical analysis such as Ki-67, p53, cytokeratin13, 17, and p16, is also helpful for the diagnosis. After surgical treatment, the resected specimens from OSCC patients are examined in details regarding prognostic factors, which are disease staging, resection margin free of diseases, tumor thickness, and extracapsular dissemination of lymph nodes. Furthermore, it is reported that EGFR-, NOTCH-, PI3K-, PTEN-and AKT-mediated pathways are involved in OSCC proliferation, suggesting that these factors can be expected to be promising molecular targets for OSCC treatment.
