Studies have revealed that CD90 could be used as a possible surface marker of LCSCs.6–8 When CD90+ cells isolated from liver cancer cell lines and liver tissues of liver cancer patients were inoculated into severe combined immunodeficiency (SCID) rats, animals developed cancer showing that these cells were carcinogenic.6 The diagnosis of primary liver cancer was also confirmed by pathological evaluation. This evidence concerns the gene THY1 and cancer.