ERBB2 and neoplasm: There were only four cases positive for ESR1 both in the primary tumor and EpCAM(+) CTCs, three cases positive for PR both in the primary tumor and EpCAM(+) CTCs, while all samples that were positive for HER2 overexpression in the EpCAM(+) CTC fractions were negative for HER2 amplification in the primary tumor.