In solid tumors, CSCs are identified by specific markers or marker combinations (e.g., CD44 and CD24 in breast cancer; CD133, CD166 and aldehyde dehydrogenase in colorectal cancer; CD133, CD44, aldehyde dehydrogenase and epithelial cell adhesion molecule in pancreatic cancer) [15]. The gene discussed is PROM1; the disease is breast carcinoma.