MYCN and Nijmegen breakage syndrome: More recently, investigators from the Children’s Oncology Group had analyzed 241 NB cases with high MKI; among the 120 MYCN-amplified high-MKI cases, 101 (84.2%) showed evidence of positive MYCN staining and were associated with worse 4-year event-free survival.9 In fact, the majority of the MYCN-amplified NBs express MYCN protein.10 However, there is also evidence that overexpression of MYCN protein can happen in cases without gene amplification and similarly appears to act as an independent poor prognostic factor.11