Immunohistochemistry was performed with anti-p53 mouse monoclonal antibody (Clone BP-53-11; Ventana Medical Systems Inc., Oro Valley, AZ) and anti-Smad4 mouse monoclonal antibody (clone B8; Santa Cruz Biotechnology Inc., Dallas, TX) and interpreted by 2 authors (D.H. and R.H.H.) as previously described.3 (link),12 (link),13 (link) Briefly, p53 immunolabeling was considered aberrant when there was diffuse nuclear labeling in >60% of cells (overexpression) or complete absence of nuclear labeling (lack of expression). Scattered nuclear labeling (wild-type) of nonneoplastic stromal cells was used as a positive internal control. Smad4 immunolabeling was considered lost when there was complete absence of nuclear and cytoplasmic labeling and intact when there was diffuse or partial nuclear and/or cytoplasmic labeling. Nuclear and cytoplasmic labeling of nonneoplastic pancreatic ductal cells and islet cells were used as a positive internal control.