Serosal invasion in TNM staging of mass‐forming intrahepatic cholangiocarcinoma

Background/Purpose The Liver Cancer Study Group of Japan established a tumor‐nodule‐metastasis (TNM) staging system for mass‐forming intrahepatic cholangiocarcinoma, with T determined by tumor number and size and vascular or serosal invasion. Serosal invasion is not considered in the designation established by the International Union Against Cancer. Methods Sixty‐three patients who underwent hepatic resection for mass‐forming intrahepatic cholangiocarcinoma were investigated retrospectively, with the investigation including univariate and multivariate analyses of potential prognostic factors. Results By log‐rank test, tumor size more than 3.0 cm, vascular invasion, lymph node metastasis, intrahepatic metastasis, and involved resection margin, but not serosal invasion, were associated significantly with poor prognosis. Even in patients with serosal invasion, the postoperative outcome was much better in those without than in those with vascular invasion. Multivariate analysis identified vascular invasion, lymph node metastasis, and an involved resection margin as independent prognostic factors. When serosal invasion was excluded from tumor staging, the 5‐year survival rates became more clearly stratified: 100% in those with stage I disease, 62% in those with stage II, 25% in those with stage III, and 7% for patients with stage IV. Conclusions Serosal invasion showed no survival impact after hepatic resection for mass‐forming intrahepatic cholangiocarcinoma. When serosal invasion was omitted from the TNM staging proposed by the Liver Cancer Study Group of Japan, stratification of postoperative survival between stages was more effective.