Moon et al. [5] previously reported that nearly all breast tumors examined (N = 24/25) had detectable NIS mRNA by RT-PCR and the extent of variation in NIS mRNA levels among tumors was about 10-fold (median 0.6 ± 0.27, range 0.10-1.27 arbitrary units). This evidence concerns the gene SLC5A5 and breast neoplasm.