Pathology of treated pancreatic ductal adenocarcinoma and its clinical implications

Context.-Preoperative neoadjuvant therapy has been increasingly used to treat patients with potentially resectable pancreatic ductal adenocarcinoma (PDAC). Neoadjuvant therapy often induces extensive fibrosis in tumor, adjacent pancreatic parenchyma, and peripancreatic tissue. Histopathologic evaluations and histologic tumor response grading (HTRG) of posttherapy pancreatectomy specimens are very difficult and challenging. Studies on prognostic significance of posttherapy pathologic staging, optimal system for HTRG, and other pathologic parameters in treated PDAC patients are limited. Objective.-This review is to provide a timely update of the prognostic values of posttherapy pathologic staging, HTRG, and other pathologic parameters in PDAC patients who received neoadjuvant therapy and pancreas resection. Data Sources.-Systemic review of major studies on pathologic evaluation and its clinicopathologic implications in treated PDAC patients. Conclusions.-Systemic pathologic examination, histologic tumor regression grading, pathologic evaluation of the margins, tumor involvement of superior mesenteric vein/portal vein, accurate pathologic staging, and reporting of posttherapy pancreatectomy specimens provide highly valuable prognostic information for postoperative patient care. Our findings suggest for the first time that tumor size of 1.0 cm, instead of 2.0 cm, is a better cutoff for ypT2 in PDAC patients. The newly proposed 3-tier MD Anderson HTRG system not only has proved to be an independent prognostic marker for PDAC patients who received neoadjuvant therapy and pancreatectomy, but also improves interobserver agreement among pathologists in evaluation of tumor response. This grading system should be considered in future editions of the College of American Pathologists protocol for PDAC.