[header] How to tell if you have mouth cancer [title] Look for ulcers and sores on your lips, tongue, cheeks and the floor of your mouth. [step] Mouth ulcers are very common and are not a surefire sign of mouth cancer in and of themselves. However, when mouth ulcers are combined with other symptoms and their development follows a certain pattern, they may indicate cancer. 
[substeps] Look for mouth ulcers which have not healed in over two or three weeks. Look for mouth ulcers that recur in the same areas of the mouth over and over again.