Tumours which are either malignant or premalignant can develop into cancer. Premalignant tumours are typically scaly and thicky patches. For example, Leukoplakia, which can be the early sign of mouth cancer, are painless, have irregular shapes, and do not go away even when the tongue is scrapped. Malignant tumours have an uncontrolled growth rate. They are formed in epithelial cells (stomach, prostate, pancreas, lung, liver, colon, or breast), in bones, cartilage, ovaries, testicles, brain, abdomen or chest.