Women with current ET use and obesity were less likely to be diagnosed with luminal A–like (OR, 0.65 [95% CI, 0.50-0.85]), luminal B–like (OR, 0.44 [95% CI, 0.25-0.76]), luminal B–ERBB2-like (OR, 0.41 [95% CI, 0.23-0.74]), or triple-negative (OR, 0.66 [95% CI, 0.43-1.00]) tumors. This evidence concerns the gene ERBB2 and obesity due to melanocortin 4 receptor deficiency.