Is that an Oral Cancer?

My father has white-yellowish patches in his mouth, actually in his cheeks for about 5-6 years. He is 51 years old. Sometimes he has lesions in his mouth, but not very often. He thinks that he has leukoplakia. He used to smoke but gave up 14 years ago. He also has dentures. Does he have an oral cancer or something precancerous? If yes, what stage? If not, what is his condition? Thank you so much.