ERBB2 and pancreatic ductal adenocarcinoma: Heterogeneous over-expression of tumor-associated receptors, such as epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER-2), and transferrin receptor (TfR), has been reported in a wide range of tumors, including pancreatic ductal adenocarcinoma (PDAC) [22,23,24] and head and neck squamous cell carcinoma (HNSCC) [25,26,27,28,29,30,31,32], in addition to breast cancers [33,34,35], ovarian cancer [36,37], non-small cell lung cancer [38,39,40,41], and bladder cancer [42,43].