A panel of putative stem cell makers was studies in a large group of different NSCLCs at histopathological level, showing a different pattern of positivity in three groups of tumors: CD44, ABC45, ALDH1 and Nestin were associated with poorly differentiated tumors; ALDH1, CD44 and SOX2 were frequently expressed in LSQCC; CD24, CD126 and epithelial cell adhesion molecule markers were expressed in adenocarcinomas [202]. Here, ALDH1A1 is linked to adenocarcinoma.