Disorders which affect the oral mucosa (the lining of the mouth) include common ulcer conditions which are not serious but which can be painful and interfere with quality of life, ranging up to more sinister conditions including oral cancers.
It must be emphasized that just because somebody has an ulcer, it does not mean that they necessarily have a cancer condition. Sometime diagnosis requires a biopsy in which a small sample is removed under local anaesthesia for examination under the microscope.