More recently, a tumor initiating cell (TIC) genomic signature derived from CD44+/CD24-/low-sorted cells and mammospheres obtained from primary human breast tumors was found to be exclusively enriched by gene expression in the claudin-low subtype [6,7], and the expression of this CD44+/CD24-/low/claudin-low profile increased in posttreatment samples after neoadjuvant chemotherapy or hormone therapy [7]. The gene discussed is CD44; the disease is breast neoplasm.