PROM1 and breast cancer: The comprehensive review of meta-analyses presented here confirms the correlation between CD133 expression and certain signs of the disease severity in many malignancies including the following: osteosarcoma, glioma, colorectal cancer, head and neck squamous cell carcinoma, hepatocellular carcinoma, non-small cell lung cancer, ovarian cancer, pancreatic ductal adenocarcinoma, gastric cancer, and breast cancer.