ALDH1A1 and neoplasm: Our study showed that CSC markers, ALDH1 and Notch1, were infrequently found in verrucous carcinoma, a result that could be justified by the indolent behavior of this tumor, whereas the strong immunopositivity of ALDH1 in poorly differentiated oral tumors, especially in the BSCCs, may indicate a higher degree of aggressiveness in the clinical behavior of these subtypes of oral cancer.