Background: Intraductal-growth (IG) type of intrahepatic cholangiocarcinoma (ICC) may be associated with a favorable prognosis compared with mass-forming (MF) and periductal-infiltrating (PI) ICC. Methods: The clinico-pathological characteristics and long-term outcomes of 1206 patients undergoing liver resection for ICC were compared based on the ICC morphological classification. Results: Compared with MF patients, IG patients had a higher incidence of poor/un-differentiated tumor, lympho-vascular, and perineural invasion (poor/un-differentiated: MF, 18% vs. IG, 24%; lympho-vascular invasion: MF, 30% vs. IG, 35%; perineural invasion: MF, 17% vs. IG, 33%; all p > 0.05). The pattern of recurrence was different among MF patients (intrahepatic only: 63%; extrahepatic only: 22%; both intra- and extrahepatic: 16%) versus IG patients (intrahepatic only: 46%; extrahepatic: 25%; both intra- and extrahepatic: 29%) (p < 0.001). Moreover, while 78% of patients with MF had an early recurrence (<18 months from surgery), 59% of IG patients had and early recurrence (p = 0.039). On multivariable analysis, after controlling for competing risk factors, IG patients had a similar prognosis as MF patients (HR 0.90, p = 0.69). Conclusion: While IG patients more frequently presented with more adverse pathological characteristics, the prognosis of IG patients was comparable with MF patients after controlling for all these adverse factors.
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