Lesions inside of the mouth are typically the first sign of mouth cancer, states the National Institute of Dental and Craniofacial Research. However, some other signs of mouth cancer to watch out for include lumps or soreness inside the mouth, difficulty chewing or swallowing, numbness and tooth pain.
There are two types of lesions: leukoplakia, which are white, and erythroplakia, which are red, according to the National Institute of Dental and Craniofacial Research. The red lesions have the greatest chance of becoming cancerous. If either type of lesion does not dissolve within two weeks of appearing, they should be evaluated by a doctor, and they may be considered for a biopsy so that a definite diagnosis can be given.