Oral Ulcer. Oral cancer is usually characterized by a non-helaing oral lesion. A recurrent ulcer that heals between events is less likely to represent oral cancer. The definitive test to diagnose oral cancer is a biopsy of any suspicious lesions. Oral biopsy is a very straightforward process that can generally be accomplished in 15 minutes with local anesthesia.
Good Clinical Exam. Most apthous ulcers or the oral cavity will run its course in a week to ten days. Herpetic ulcers may completely disappear and reappear in the same location. The oral cancer lesion will usually not be a lesion that disappears and reappear in a different location. The oral cancer lesion will often have an rolled raised border with a crusty or inflamed appearance, and feel indurated.
Time. Oral ulcers will usually be healed and gone in 7-10 days. If you have an ulcer or sore that has been around significantly longer than that, you need to have it checked.
Oral Cancer. The only way to know conclusively whether or not a lesion is cancerous or not is by having the area biopsied and sent for microscopic evaluation to a pathologist. While most ulcers are gone by two weeks, there are some types of ulcers that last longer but are not cancerous. Some cancers do not ulcer. Start by seeing your dentist or an oral surgeon for an evaluation and diagnosis.