We did not observe any association between the A10398G polymorphism in the mitochondrial ND3 gene and breast cancer risk in either the NHS (Odds Ratio (OR) 1.01, 95% Confidence Interval (CI) 0.85–1.19) or WHS (OR 0.94, 95% CI 0.72–1.22) (Table 1). This evidence concerns the gene MT-ND3 and breast carcinoma.