Interestingly, in the only neuroblastoma patient that showed CD271−/+lo tumor cells, CD271 expression was restricted to the primary tumor, while negative in metastatic BM cells; this could potentially be due to a different degree of tumor cell maturation at both sites, absence of CD271 being associated with a more immature and aggressive tumor behavior [57]–[58]. Here, NGFR is linked to neuroblastoma.