Our review of all publications on the role of OPN in cancers of children and young adults has shown that the monitoring of OPN protein level in serum and cerebral-spinal fluid of children with acute lyphoblastic anemia with CNS involvement and in patients with highly malignant brain tumors, reflected the tumor bulk and the response to CHT (Karpinsky et al. 2017). The gene discussed is SPP1; the disease is brain neoplasm.