White, red, or mixed white-red areas that are not easily wiped away, persist for more than 2 weeks, and are not definable as some other condition may be precancerous. The same risk factors are involved in precancerous changes as in cancerous growths, and precancerous changes may become cancerous if not removed.
Leukoplakia is a flat white spot that may develop when the moist lining of the mouth (oral mucosa) is irritated for a long period. The injured spot appears white because it has a thickened layer of keratin—the same material that covers the skin and normally is less abundant in the lining of the mouth.
Erythroplakia is a red and flat or worn away area that results when the lining of the mouth thins. The area appears red because the underlying capillaries are more visible. Erythroplakia is a much more ominous predictor of oral cancer than leukoplakia.
Last full review/revision November 2006 by Robert B. Cohen, DMD