Background. The present study was conducted to clarify the pathological factors in patients who underwent surgery for mass-forming type intrahepatic cholangiocarcinoma (IHC). Methods. From 1982 to July 2004, a total of 60 liver resections for mass-forming type IHC were performed at Kyushu University and its affiliated institutions. Portal venous, lymphatic, hepatic venous, and serosal invasion was examined by univariate and multivariate analyses for their prognostic value. The portal venous (PV) invasion index was defined as follows: PV0, portal venous invasion (-) and intrahepatic metastasis (-); PV1, portal venous invasion (+) or intrahepatic metastasis (+); PV2, portal venous invasion (+) and intrahepatic metastasis (+). The lymphatic invasion (LI) index was defined as follows: LI0, lymphatic duct invasion (-) and lymph node metastasis (-); LI1, intrahepatic lymphatic duct invasion (+) or lymph node metastasis (+); LI2, intrahepatic lymphatic duct invasion (+) and lymph node metastasis (+). Results. In univariate analysis, statistically significant prognostic factors for poor outcome were tumor size (>5 cm), serosal invasion (+), PV1 or PV2, LI1 or LI2, histological grade (moderate and poor), hepatic venous invasion (+) and noncurative resection. After multivariate analysis, the lymphatic invasion index and histological grade were statistically independent prognostic factors for overall survival and recurrence-free survival. Conclusions. In patients with mass-forming type IHC, lymphatic invasion is the most important invasion pathway, compared with serosal and portal and hepatic venous invasion. Stratification of the lymphatic invasion pathway by lymphatic invasion, including intrahepatic lymphatic duct invasion and lymph node metastasis, is a good predictor for prognosis in patients after hepatectomy for massforming type IHC.
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