Oral cancer, also known as mouth cancer, is a type of head and neck cancer and is any cancerous tissue growth located in the oral cavity. It may arise as a primary lesion originating in any of the tissues in the mouth, by metastasis from a distant site of origin, or by extension from a neighbouring anatomic structure, such as the nasal cavity. Alternatively, the oral cancers may originate in any of the tissues of the mouth, and may be of varied histologic types: teratoma,adenocarcinoma derived from a major or minor salivary gland, lymphoma from tonsillar or other lymphoid tissue, or melanoma from the pigment-producing cells of the oral mucosa. There are several types of oral cancers, but around 90% are squamous cell carcinomas, originating in the tissues that line the mouth and lips. Oral or mouth cancer most commonly involves the tongue. It may also occur on the floor of the mouth, cheek lining, gingiva (gums), lips, or palate (roof of the mouth). Most oral cancers look very similar under the microscope and are called squamous cell carcinoma, but less commonly other types of oral cancer occur, such as Kaposi's sarcoma.

Risk factors for the development of oral cancer include:
a. Smoking . Cigarette, cigar, or pipe smokers are six times more likely than non-smokers to develop oral cancers.
b. Smokeless tobacco users. Users of dip, snuff, or chewing tobacco products are 50 times more likely to develop cancers of the cheek, gums, and lining of the lips.
c. Excessive consumption of alcohol. Oral cancers are about six times more common in drinkers than in non-drinkers.
d. Family history of cancer.
e. Excessive sun exposure, especially at a young age.
f. Human papillomavirus (HPV). Certain HPV strains are etiologic risk factors for Oropharyngeal Squamous Cell Carcinoma (OSCC)

It is important to note that over 25% of all oral cancers occur in people who do not smoke and who only drink alcohol occasionally.