Oral cancers appear as red or white patches of mouth tissue or small ulcers that look like canker sores but are painless. Oral cancers usually form on the tongue or floor of the mouth but can occur on any tissue in and around the mouth. This includes cancers of the tonsils, adenoids, uvula (soft palate), roof of the mouth (hard palate), inside the lining of the cheeks, the gums, teeth, lips, the area behind the wisdom teeth, and salivary glands. Some of these lesions may be benign, others may be malignant, and others may be precancerous. The most common type of precancerous cells in the mouth are:

• Leukoplakias: Leukoplakias consist of thick, white lesions that most commonly form beneath or around the tongue, cheeks, or gums. These mouth sores are most often seen in tobacco users.
• Erythroplakias: These lesions appear as a red, raised area in the mouth and have a higher incidence of becoming malignant than leukoplakias.

A biopsy is often needed to diagnose leukoplakias and erythroplakias.

Squamous cell carcinomas are the most common type of oral cancer. Less common are lymphoma and salivary gland cancers. Most oral cancers occur in people age 45 and older. When cancers of the mouth metastasize, they are most likely to spread to the lymph nodes in the neck.