Neuroblastoma and PNET were those tumors which displayed the highest CD56 levels, supporting the utility of CD56 both to discriminate non-hematopoietic vs. hematopoietic neoplasms [31], [34], and for the differential diagnosis between distinct subtypes of CD45− non-hematopoietic pediatric solid tumors. This evidence concerns the gene NCAM1 and primitive neuroectodermal tumor.