Overexpression of CD44 within numerous tumours, such as mucoepidermoid carcinoma, salivary gland tumours, breast cancer, gliomas, renal carcinoma, gallbladder cancer, cholangiocarcinoma, gastric cancer, ovarian cancer, bladder carcinoma, pancreatic tumours, colorectal cancer and oral cancer has been associated with increased tumorigenicity and decreased overall survival, indicating a poorer prognosis. Here, CD44 is linked to breast cancer.