Oral cancer or mouth cancer,
[1] a type of head and neck cancer, is any cancerous tissue growth located in the oral cavity.

[2]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 neighboring 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.

SYMPTOMS:-
On the tongue, lip, or other mouth areas
Usually small
Most often pale colored, may be dark or discolored
Early sign may be a white patch (leukoplakia) or a red patch (erythroplakia) on the soft tissues of the mouth
Usually painless initially
May develop a burning sensation or pain when the tumor is advanced
Behind the wisdom tooth
Even behind the ear
Additional symptoms that may be associated with this disease:

Tongue problems (moving it)
Swallowing difficulty
Mouth sores
Pain and paraesthesia are late

CAUSES:-
Around 75 percent of oral cancers are linked to modifiable behaviors such as tobacco use and excessive alcohol consumption. Other factors include poor oral hygiene, irritation caused by ill-fitting dentures and other rough surfaces on the teeth, poor nutrition, and some chronic infections caused by bacteria or viruses. If oral cancer is diagnosed in its earliest stages, treatment is generally very effective.