Other important points to note are that breast cancers that have high histologic grades, are ER negative and have high Ki-67 proliferation indices, are prone to achieve pCR following PST, as demonstrated in many previous studies (Ellis et al, 1998; Chang et al, 1999; Rouzier et al, 2005; Carey et al, 2007) and that ER-negative cancers, especially basal-like breast cancers, are enriched in CSCs (Honeth et al, 2008; Morimoto et al, 2009; Nalwoga et al, 2010; Park et al, 2010). Here, MKI67 is linked to breast cancer.