SLC6A2 and neoplasm: Metaiodobenzylguanidine (mIBG) is a guanethidine derivative and an analogue of norepinephrine and is therefore specifically taken up and stored in tumours derived from tissues of sympathetic nervous system origin, which express the norepinephrine transporter (Mairs et al, 1994; Boyd et al, 1999; McCluskey et al, 2005; Moroz et al, 2007).