ALDH1A1 and neoplasm: RT-PCR did not reveal any change in ALDH1A1 expression level but confirmed an increased level of CD44 expression in tumor tissue of smokers and nonsmokers, while IHC study demonstrated that CD44 is expressed not only by normal and tumor epithelial cells but also by cells of the organ stroma, which casts doubt on the possibility of using this receptor to mark specific populations of tumor cells.