Previously, studies have shown that CSCs from human primary HNSCC tissues or SCC cell lines have elevated aldehyde dehydrogenase (ALDH) activities.[14] Using an ALDEFLUOR kit, we sorted ALDHlow nonstem tumor cells and ALDHhigh CSC‐like cells with the specific ALDH inhibitor diethylaminobenzaldehyde (DEAB) as a control (Figure S3B, Supporting Information), and found that the circFAT1 expression was significantly higher in ALDHhigh CSCs than in ALDHlow tumor cells (Figure 3E). Here, LDHA is linked to neoplasm.