PHOX2B and adrenal gland neoplasm: Since the MicroNB and MacroNB variants share a common genetic background but initially originated from different microenvironments (the MicroNB cells originated from adrenal tumors and the MacroNB cells originated from lung metastasis) [17, 18], it is not unlikely that the differential expression of PHOX2B in these cells is due to genetic or epigenetic events that took place in the different microenvironments from which these variant progenitors were generated.