CD44 and adenoma: CD44v6 and other ‘variable’ CD44 isoforms (CD44v4-10) earmark Lgr5+ intestinal stem cells (ISCs), that is, the cells of origin of intestinal tumors, and accordingly promote adenoma formation in vivo (Zeilstra et al., 2008; Zeilstra et al., 2014; Misra et al., 2009).