We observed a significant difference between the percentage immunostained nuclei for NFκB1 between ER+ (42.20%) and ER− (61.20%) breast tumours (P=0.002) For RelB, a trend towards a significant difference in the percentage of immunostained nuclei was observed (RelB immunostained nuclei in ER+ breast tumours: 29.60%, RelB immunostained nuclei in ER− breast tumours: 52.30%; P=0.092). This evidence concerns the gene NFKB1 and breast neoplasm.