With the help of the MBB buffer, we determined the HER2 ECD levels in serum samples from invasive breast cancer patients (“breast ca”, N=28), non-invasive DCIS patients (“DCIS”, N=33), patients with benign breast disease (“benign”, N=11), as well as healthy controls (“control”, N=29) (Figure 1). Here, ERBB2 is linked to ductal breast carcinoma in situ.