OUTLINE: Archived tumor tissue and serum samples are analyzed for neuropeptide Y and its receptors (Y1, Y2, and Y5) expression, neuroblastoma prognostic factors (MYCN, TrkA, TrkAIII, TrkB, BDNF, and NGF), and angiogenic markers by real-time PCR, IHC, ELISA, radioimmunoassay (RIA), mitogenic assay, caspase 3/7 activity assay, western blots, liquid chromatography, tandem mass spectrometry, proteomic assays, and other assays. Results are then analyzed and compared with patients' clinical data, including stage of disease, its phenotype, prognostic markers, age and gender, and response to treatment.