Histopathological characteristics of hypervascular cholangiocellular carcinoma as an early stage of cholangiocellular carcinoma

Aim Prognosis of hypervascular cholangiocellular carcinoma (h‐ CCC ) is reportedly better than that of ordinary hypovascular CCC (o‐ CCC ). The aim of this study is to clarify the histopathological characteristics of h‐ CCC . Methods On the basis of the findings in the arterial phase of contrast‐enhanced computed tomography, 16 cases of mass‐forming‐type CCC were divided into two groups (h‐ CCC , n  = 8; o‐ CCC , n  = 8). Areas of high ( A rea H ‐a) and low ( A rea H ‐b) attenuation in h‐ CCC cases and areas of low attenuation in o‐ CCC cases ( A rea O ) were delineated. These areas were then evaluated histopathologically to determine the proportion of tumor cells, fibrous stroma, arterial vessel density, and immunohistochemical expression of Vascular endothelial growth factor; angiopoietin‐2; cytokeratin 7, CK19 , SOX9 and SOX17 genes; epithelial cell adhesion molecule; and the B mi‐1, K i‐67, epithelial membrane antigen and polyclonal carcinoembryonic antigen.Results The areal ratio of tumor cells decreased and that of fibrous stroma increased in the following order: A rea H ‐a, A rea H ‐b and A rea O . Values for AVD and neural cell adhesion molecule positivity rate were significantly higher in A rea H ‐a than in A reas H ‐b or O . Expressions of vascular endothelial growth factor and angiopoietin‐2 were significantly higher in A reas H ‐a and H ‐b than in A rea O . The K i‐67 labeling index increased in the following order: A rea H ‐a, A rea H ‐b and A rea O . Conclusion A high areal ratio of tumor cells and AVD as well as a high expression of stem cells and angiogenic markers were observed in cases of h‐ CCC , whereas the areal ratio of fibrous stroma and malignant potential were low. These results suggest that h‐ CCC may represent the early stage of CCC .