Activation of the mitogen/extracellular signal-regulated kinases (MEK1/2)/extracellular signal-regulated kinases (ERK1/2) was also frequently observed in NB [10], and a low frequency of missense mutations of genes in the Ras-Raf-MEK/ERK pathway has been reported in NB [5, 6, 12]. The gene discussed is MAPK3; the disease is neuroblastoma.