CD44 and brain neoplasm: The main function ascribed to CD44 is acting as a receptor for HA—the key component of ECM in the brain playing a crucial role in many physiological and pathological processes, such as the neuronal development, synaptic plasticity (e.g., learning and memory), epileptogenesis, response to injury, neurodegeneration and brain tumour invasion (Kochlamazashvili et al., 2010; Wlodarczyk et al., 2011).