CD44 and breast cancer: While that article was retracted due to technical inaccuracies that affected the overall significance of the results, substantial primary evidence remains, indicating that CD44 variants, particularly CD44v9, are prognostic indicators of poor survival in patients with head and neck cancer [65], multiple myeloma [66], gastric cancer [67,68], upper-tract urothelial cancer [69], hepatocellular carcinoma [70], colorectal cancer [71], bladder cancer [72], pancreatic cancer [73], gallbladder cancer [74], and breast cancer [75].