ERBB2 and breast carcinoma: Currently, measuring somatic mutations, such as those observed in the Kirsten rat sarcoma viral oncogene homologue gene (KRAS) [9], and copy number variations, such as human epidermal growth factor receptor 2 (ERBB2, formerly known as HER2) amplification in breast cancer [10] or foetal aneuploidy [11] in cfDNA, show considerable clinical potential.