ESR1 and breast cancer: It is important to recognize that the association found between THRβ1 expression and BC-specific survival was found only among patients with ER+ tumors and not among those with ER- disease; further, ER+ tumors were more likely to have high THRβ1 expression than ER- tumors (92.4% vs. 7.6%, p  <  0.0001) [11].