The subtracted library of cDNAs down-regulated in the MCF-7 cells relative to the Huma 123 cells contained a cDNA corresponding to the mRNA for an EF-hand protein, S100A2, which was shown previously to be abundantly expressed in both normal breast and benign breast tumour specimens (Liu et al, 2000), but only detectable in less than 15% of malignant breast cancer specimens tested. Here, S100A2 is linked to breast benign neoplasm.