CA9 and breast cancer: One such group, the basal-like breast cancers (BLBC), expresses minimal levels of ER/PR/HER2 and high levels of CK 5/6, CK 14, CK 17, p-cadherin, caveolin-1, carbonic anhydrase IX gene (CA IX), p63 (a member of the p53 family of transcription factors and a myoepithelial stem cell regulator), and epidermal growth factor receptor (EGFR or HER1) similar to their cell of origin in normal breast tissue [11].