Mouth cancer has the same meaning as oral cancer - it is a cancer that occurs in any part of the mouth; on the tongue's surface, in the lips, inside the cheek, in the gums, in the roof and floor of the mouth, in the tonsils, and also the salivary glands.
Most patients have no detectable symptoms during early stages of oral cancer. Smokers, heavy drinkers should have regular checkups at the dentists' - dentists are often able to identify signs of oral cancer.
Depends on various factors, such as where the cancer is, its stage, as well as the patient's general health.