Oral cancer may form in any of three main areas:
Most oral cancers start in squamous cells (thin, flat cells) that line the lips, oral cavity, and oropharynx. Cancer that forms in squamous cells is called squamous cell carcinoma. Lesions on the mucous membranes (the lining of the mouth and throat), including leukoplakia (an abnormal white patch of cells) and erythroplakia (an abnormal red patch of cells), may develop into squamous cell carcinoma.
In Western countries, such as the United States, the most common areas for oral cancer are the tongue and the floor of the mouth. In parts of the world where chewing tobacco or betel nuts is common, oral cancer often forms in the retromolar trigone and buccal mucosa.