The authors found no difference in the baseline total plasma cell-free DNA or HER-2 gene-copy number compared to healthy controls, and no difference in baseline plasma HER-2 gene-copy number between tissue HER-2-positive and -negative patients; nor were they able to detect gene amplification in plasma in the tissue HER-2-positive patient group with primary breast cancer. The gene discussed is ERBB2; the disease is breast carcinoma.