Pancreatic intraglandular metastasis predicts poorer outcome in postoperative patients with pancreatic ductal carcinoma

Intraorgan metastasis of a primary cancer within the organ of origin, such as intrahepatic metastasis of hepatocellular carcinoma, is one of the key features for clinicopathologic staging of the cancer. Pancreatic intraglandular metastasis (P-IM) of pancreatic ductal carcinoma (PDC) is encountered occasionally but has not yet been evaluated. The aim of this study was to investigate the clinicopathologic characteristics and prognostic value of P-IM in patients with PDC. The histopathologic features of 393 consecutive patients with PDC who had undergone pancreatic resection at the National Cancer Center Hospital, Tokyo, between 2003 and 2010 were reviewed. For the purposes of the study, P-IM was defined as an independent tumor showing histopathologic features similar to those of the primary one. Twenty-six cases of P-IM were identified in 21 (5.3%) of the reviewed patients. The incidence of P-IM at each stage of the TNM classification was 0% (0/7) at stage IA, 17% (1/6) at stage IB, 5% (5/92) at stage IIA, 4% (11/252) at stage IIB, 0% (0/1) at stage III, and 11% (4/35) at stage IV. Univariate survival analysis showed that both overall survival and disease-free survival for patients with P-IM were significantly shorter than for those without P-IM (P>0.001 and P=0.019, respectively). Multivariate survival analysis showed that P-IM was significantly correlated with shorter overall survival (P=0.002; hazard ratio=2.239; 95% confidence interval: 1.328-3.773). Our findings suggest that the presence of P-IM in patients with PDC is an independent prognosticator and may represent aggressive tumor behavior.