Histopathologic Basis for the Favorable Survival after Resection of Intraductal Papillary Mucinous Neoplasm-Associated Invasive Adenocarcinoma of the Pancreas

Objective: To identify pathologic features that may account for the favorable survival after resection of invasive pancreatic adenocarcinoma arising in the setting of intraductal papillary mucinous neoplasm (IPMN) compared with standard pancreatic ductal adenocarcinoma (PDA) in the absence of IPMN. Summary Background Data: The 5-year survival after resection of IPMN-associated invasive adenocarcinoma is reported to be between 40% and 60%, which is superior to the 10-25%, typically cited after resection of standard PDA. It remains unclear whether this represents distinct biology or simply a tendency for earlier presentation of IPMN-associated invasive adenocarcinoma. Methods: A single institution's prospective pancreatic resection database was retrospectively reviewed to identify patients with invasive pancreatic adenocarcinoma who underwent pancreatectomy with curative intent. Log rank and Cox regression analysis were used to identify factors associated with survival. Results: From 1995 to 2006, 1260 consecutive patients were identified, 132 (10%) with IPMN-associated invasive adenocarcinoma and 1128 (90%) with standard PDA. Actuarial 5-year survival was 42% after resection for IPMN-associated versus 19% for standard PDA (P < 0.001). However, compared with standard PDA, invasive adenocarcinoma arising within an IPMN was associated with a lower incidence of (1) advanced T stage (T-2-T-4, 96% vs. 73%, P < 0.001); (2) regional lymph node metastasis (78% vs. 51%, P < 0.001); (3) poor tumor differentiation (44% vs. 26%, P < 0.001); (4) vascular invasion (54% vs. 33%, P < 0.001); (5) perineural invasion (92% vs. 63%, P < 0.001); and (6) microscopic margin involvement (28% vs. 14%, P < 0.001). Specifically, in the presence of any one of the aforementioned adverse pathologic characteristics, outcomes after resection for IPMN-associated and standard PDA were not significantly different. Conclusion: The favorable biologic behavior of IPMN-associated compared with standard PDA is based on its lower rate of advanced T stage, lymph node metastasis, high tumor grade, positive resection margin, perineural, and vascular invasion. In the presence of any one of the aforementioned adverse pathologic characteristics, however, survival outcomes after resection of IPMN-associated and after resection of standard pancreatic adenocarcinoma are similar.