Immunohistochemistry as a surrogate to molecular diagnosis in pancreatic tumors

Molecular and genomic characterization of the major neoplasms of the pancreas has produced a wealth of information and insight into the genetics involved in tumor initiation and progression. Many of these genetic discoveries can be interrogated with cost-effective immunohistochemical stains, which include: p53, Smad4, and mismatch repair proteins in pancreatic ductal adenocarcinomas; DAXX and ATRX in well-differentiated pancreatic neuroendocrine tumors; β-catenin and LEF1 in solid-pseudopapillary neoplasms; and, STAT6 in intrapancreatic solitary fibrous tumors. When combined with the gross and morphologic findings, the aforementioned immunohistochemical markers can enhance the diagnosis and prognostication of these neoplasms. The focus of this review is to explore the key molecular and genomic alterations that can be reliably assessed by immunohistochemistry in pancreatic neoplasms and discuss their clinical and pathologic applications.