ERBB2 and breast cancer: PC1 was inversely associated with a risk of all five breast cancer sub-types, of which associations were most consistent for HER2+ (IVWrandom-effects OR = 0.81 [95% CI: 0.67–0.99]; p-value = 0.043) and triple negative sub-types (IVWrandom-effects OR = 0.82 [95% CI: 0.73–0.91]; p-value < 0.001) (Figure 2).