Our results suggested that breast cancer patients with higher histological grade were likely to have a larger amount of SIX1 (OR: 1.50, 95% CI: 1.23–1.82; P = 0.177 and I2 = 28.1%; Fig. 3A), SIX2 (OR: 1.50, 95% CI: 1.23–1.83; P = 0.844 and I2 = 0.0%; Fig. 3B), or SIX3 (OR: 1.31, 95% CI: 1.07–1.60; P = 0.174 and I2 = 30.5%; Fig. 3C) at mRNA level. The gene discussed is SIX1; the disease is breast cancer.