ALDH1A1 and neoplasm: Recently, accumulating evidence suggested that cancer stem cells (CSCs), a small heterogeneous cell population within tumour tissues or cancer cell lines, endowed with stemness phenotypic features including enhanced self‐renewal ability in vitro and in vivo and resistance to chemotherapy and high expression levels of stemness‐associated markers, such as ALDH1, CD133, Sox2 and Oct4, might be responsible for tumour recurrence and metastasis in cancer patients irrespective of comprehensive anti‐cancer therapies, including chemoradiotherapy, targeted therapy and immunotherapy.4, 5, 6