Most nonductal histological tumors were associated with lower proportions of ERBB2-low breast cancer than ductal cancers, including lobular (aOR, 0.73; 95% CI, 0.72-0.74; P < .001), mucinous (aOR, 0.51; 95% CI, 0.49-0.52; P < .001), and metaplastic (aOR, 0.53; 95% CI, 0.50-0.56; P < .001) cancers. The gene discussed is ERBB2; the disease is cancer.