BM-infiltrating NB cells can also be detected in the cytospin of BM aspirates by immunocytochemistry with an anti-GD2 antibody [22] and by quantitative RT-PCR analysis for NB-specific mRNAs, such as tyrosine hydroxylase (TH), the first enzyme in the synthesis of catecholamine, and the paired-like homeobox 2b (PHOX2B), expressed at early stages during neuronal development [23]. The gene discussed is PHOX2B; the disease is neuroblastoma.