However, subgroup analysis showed that, in HER2(+) breast cancer patients, a negative correlation existed between FT3 levels and Ki67 (r = −0.60 and P = 0.004) but not between Ki67 and FT4 (r = 0.04 and P = 0.85) or TSH (r = −0.23 and P = 0.30) (Figure 2). Here, ERBB2 is linked to breast cancer.