ERBB2 and neoplasm: High serum concentrations of HER2 ECD have been associated with HER2 overexpression [34], increased tumor burden [35], poorer survival [36] and resistance to endocrine therapy and chemotherapy [12,37,38], We found that HER2 ECD positivity was significantly associated with most clinicopathological parameters including tumor size, lymph node involvement, tumor stage, histological grade, chromosome ploidy, ER, PR, and HER2/neu membrane protein overexpression.