MYCN and neuroblastoma: For CCG/COG (Children's Cancer Group/Children's Oncology Group) neuroblastoma studies prior to the INRG stratification, in addition to clinical stage, other factors, including age, amplification of the MYCN oncogene and tumor histology (Shimada classification), were used in assigning risk groups (high-risk, intermediate-risk, or low-risk) [14, 15].