Objective: We compared the pathological features and stage-matched outcomes of patients with invasive intraductal papillary mucinous carcinoma (IPMC) and invasive ductal carcinoma (IDC) of the pancreas to identify the reasons for these diseases’ differing prognoses. Methods: We analyzed 114 and 560 patients who underwent curative pancreatectomy for invasive IPMC and IDC, respectively, and analyzed their clinicopathological factors. Results: The disease-specific survival (DSS) of patients with invasive IPMC was significantly superior to that of patients with IDC exhibiting all pathological types at all stages. The DSS of patients with invasive IPMC exhibiting tubular adenocarcinoma was significantly superior to that of their counterparts with IDC only among those with stage IIB (p =.045). When comparing patients with stage IIB tubular adenocarcinoma-type invasive IPMC to their counterparts with IDC, the tumor size (2.6 cm vs. 3.3 cm, p =.010), serum level of carbohydrate antigen 19-9 (253 vs. 474 U/mL, p =.035), number of metastatic lymph nodes (3.1 vs. 4.5, p =.033), vascular invasion rate (14% vs. 41%, p =.0019) and local invasion rate (79% vs. 95%, p =.0045) were lower in the former group. Moreover, the frequency of pathological tubular adenocarcinoma grade 1 was higher in patients with invasive IPMC than in those with IDC (38% vs. 12%, p =.0004) as was the R0 resection rate (90% vs. 65%, p =.0027). Conclusions: In pathological type- and stage-matched analyses, invasive IPMC was associated with a better prognosis than IDC only in patients with stage IIB, as factors governing tumor aggressiveness were milder in the former group than in the latter.
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