Quantitative PCR (qPCR) has been used to determine HER2 amplification status in tumour DNA and has shown similar results to FISH, and some discordance with tissue-based IHC (Kulka et al, 2006; Monego et al, 2007); however, the method has not been applied previously to circulating free DNA (cfDNA). Here, ERBB2 is linked to neoplasm.