Objectives: Although intestinal-type intraductal papillary mucinous carcinoma (IPMC) is reported to have a better prognosis, few studies have addressed its invasive pattern. The meaning of "minimal invasion" (MI) in IPMC also remains unclear. We investigated the prognosis of intraductal papillary mucinous neoplasm (IPMN) focusing on MI and subtypes. Methods: We evaluated 71 patients with IPMC among a total of 179 patients with resected IPMN. Results: Although 2 of 10 MI-IPMC patients had lymph node metastasis, there were no disease-specific deaths among the MI-IPMC patients. Minimally invasive IPMCs were more frequently observed in intestinal-type IPMC (23/33 cases) than in non-intestinal-type IPMCs (16/38 cases; P = 0.019). Among 32 patients with massively invasive IPMC, the prognosis was significantly better for patients with intestinal-type IPMC than for patients with non-intestinal-type IPMC (P = 0.013). When confined to massively invasive IPMC, tubular invasion (P < 0.001) and lymphatic (P = 0.001) or serosal (P = 0.021) invasion were less frequently observed in intestinal-type IPMC than in non-intestinal-type IPMC. Conclusions: Invasive carcinoma derived from intestinal-type IPMN is associated with MI, colloid carcinoma, and less invasive behavior.
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