Recent studies show that the cells in a hybrid E/M phenotype (identified by CD24+/CD44+) can form much more tumours than those in a purely mesenchymal phenotype (identified by CD24−/CD44+), especially when the hybrid E/M phenotype is stabilized, for instance, by ‘phenotypic stability factor’ [36] such as OVOL [33,37–40]. The gene discussed is CD44; the disease is neoplasm.