Genetic changes that contribute to carcinogenesis include activation of oncogenes and inactivation of tumor suppressor genes.
Since the process of carcinogenesis is thought to occur as a stepwise accumulation of genetic alterations, it is important to select the precancerous lesions to detect an early event for the tumor formation. The study of premalignant lesions became feasible with a recent modified microdissection technique that allows the procurement of tissue from microscopic lesions for genetic analysis.