CD44 and breast cancer: Interestingly, CD44 protein has been linked to invasion, metastasis, and increased aggressiveness in several solid and hematological malignancies, such as breast cancer, hepatocarcinoma, non-Hodgkin lymphoma, or acute myeloid leukemia, among others [13,14], and it has been identified as a prognostic factor in osteosarcoma, breast cancer, ovarian cancer, gastric cancer, and gallbladder cancer [14,15,16,17,18,19].