Precancerous states of the oral mucosa refers to pathologies in which there is a risk of malignancy development, compared to normal mucosa. Some histological alterations characteristic of precancerous lesions can be easily detected in a biopsy of the lesion, allowing their classification, and hence adequate treatment. A systematic examination of the oral mucosa in patients is recommended, especially in patients who show risk factors such as tabagism and/or alcohol consumption, in order to contribute to a decrease in the incidence of malignant tumor of the oral cavity.