rs3803662 tags for a linkage disequilibrium block spanning the 5′ regulatory sequences of the gene TOX3 (TOX high mobility group box family member 3) and the 3′ region of the neighbouring hypothetical gene LOC643714. A second genome wide association study [2] identified a significant association between the T allele of rs380662 and the development of oestrogen receptor (ER) positive breast cancer. Here, TOX3 is linked to breast cancer.