As expected, both aHER2 and sHER2 were below their respective normal thresholds in healthy donors and patients bearing miscellaneous tumors (Fig. 1c), whereas either or both were above threshold in a minority (7 and 9 of 37, e.g. 19% and 24% respectively) of pre-treated HER2-positive breast cancer patients (Fig. 1d), as described for aHER2 [16]. Here, ERBB2 is linked to breast cancer.