【 Etiology】 Etiology likely to be multifactorial Tobacco smoking or snuff dipping aLcohol Betel quid usage o Mutation of the p53 gene iDiopathic Department of Oral Pathology, Shandong University 8Department of Oral Pathology, Shandong University 8 【Etiology 】 Etiology likely to be multifactorial Tobacco smoking or snuff dipping Alcohol Betel quid usage Mutation of the p53 gene Idiophathic