MYCN and neuroblastoma: The low-MKI group, indeed, had the lowest incidence of MYCN gene amplification (7.14% low MKI v 59% high MKI; P < .01) and included all three discordant cases—the two previously discussed cases that had weak IHC staining but no gene amplification, and the one MYCN-amplified NB that lacked protein expression.