Invasive carcinoma arising in intraductal papillary mucinous neoplasms of the pancreas: A matched control study with conventional pancreatic ductal adenocarcinoma

Objective: The purpose of this study was to characterize the clinicopathological features of invasive carcinomas arising in intraductal papillary mucinous neoplasms of the pancreas (IPMN) by histological subtype of the invasive component and to compare the outcomes of these patients to a cohort of matched patients with conventional ductal pancreatic adenocarcinoma. Background: Two distinct histological subtypes of invasive carcinomas arising in IPMNs have been described, colloid carcinoma and tubular carcinoma. Previous reports have suggested prognostic differences between these 2 subtypes but a matched comparison of colloid carcinoma, tubular carcinoma, and conventional pancreatic adenocarcinoma has not been reported. Methods: The clinicopathological variables of 59 patients resected for an invasive component of IPMN were analyzed with detailed pathologic review of histopathologic subtype (colloid carcinoma and tubular carcinoma). Using a postresection pancreatic adenocarcinoma nomogram, patients with either tubular or colloid carcinoma were matched on a 1:1 basis with patients resected for conventional ductal pancreatic adenocarcinoma. Clinicopathological factors and overall outcome was analyzed between the matched groups. Results: Fifty-nine patients underwent resection for IPMN with an associated invasive carcinoma (IPMN-INV). The estimated 3- and 5-year survival rates were 76% and 68%, respectively. Tubular carcinoma was present in 35 patients (59%) and 24 patients (41%) had colloid carcinoma. Tubular carcinoma subtype [hazard ratio (HR) 3.7, 95% confidence interval (CI) 1.2-11.6] and the presence of positive regional lymph nodes (HR 3.2 95% CI 1.2-8.2) were clinicopathological factors predictive of decreased survival by multivariate analysis. The 5-year estimated survival rates for tubular carcinoma and colloid carcinoma were 55% and 87%, respectively (P = 0.01). When compared with patients with conventional ductal pancreatic ductal adenocarcinoma resected during the same time period matched by a prognostic nomogram, patients with colloid carcinoma had a significantly longer survival outcome compared with patients with conventional adenocarcinoma (P = 0.0001). By contrast, survival after resection between patients with the tubular subtype (3-year estimated survival, 61%) and the matched group with conventional adenocarcinoma (3-year estimated survival, 21%) (P = 0.87) was not statistically different. Conclusions: In this study, the colloid carcinoma histological subtype of invasive IPMN had a more statistically favorable survival outcome than the tubular subtype. Patients with invasive tubular IPMN had no statistically significant difference in survival as matched patients with conventional ductal pancreatic carcinoma.