MYCN (V-myc myelocytomatosis viral-related oncogene, neuroblastoma derived) amplification, associated with spontaneous NB and found in about 20% of all NBs, is associated with a poor prognosis [4,129,130]; although children with tumors without MYCN amplification can also do poorly [131,132]. This evidence concerns the gene MYCN and Nijmegen breakage syndrome.