While surface CD24 is observed in subsets of T-ISC from liver (Lee et al, ), colon (Yeung et al, 2010) and pancreas (Li et al, 2007), the T-ISC phenotype described for primary breast cancers show negative or low level surface CD24 (CD44+CD24neg/low; Al Hajj et al, 2003). This evidence concerns the gene CD44 and breast cancer.