Some research has shown that patches on the floor of the mouth and the underside or sides of the tongue are more likely to be cancerous. However, not all studies agree that location is an important factor. The size of a patch has no link to whether it may become cancerous. Factors that are strong indicators of leukoplakia transforming to cancer include the appearance of: Nodules. White or red masses with a pebbled appearance. Ulceration. Increased firmness. Bleeding.