In addition to HER2/neu status of the tumor tissue, the extracellular domain (ECD) of HER2 (HER2 ECD), which is shed from the HER2/neu receptor after a proteolysis process, has been shown to show a better correlation with tumor burden, treatment response, disease-free status and overall survival than the full-length HER2/neu [10]. This evidence concerns the gene ERBB2 and neoplasm.