Second, especially in reference to pediatric malignancies that have the lowest mutation rates of all cancers (14), there may be no single target that can sufficiently define a cellular target as being “cancer” or “normal.” For example, in our previous gene expression profiling work, the top 3 transcripts overexpressed in stage 4 neuroblastoma were SLC10A4, CHRNA3, and SLC29A4 (13). The gene discussed is SLC29A4; the disease is cancer.