CD44 and breast carcinoma: ALDH1 activity is very infrequent in CD44+CD24neg/low breast cancer cells (Charafe-Jauffret et al, 2009; Croker et al, 2008; Ginestier et al, 2007), and populations enriched for both aldefluor activity and CD44+CD24neg/low show a high T-ISC frequency (Ginestier et al, 2007).