In our present study, CoCC was diagnosed when small gland-forming cells proliferated on pathological findings, and these CoCC cells were further confirmed by membranous positive staining for MUC-1 and/or EMA, because the usefulness of these staining patterns for confirming CoCC cells, normal ductules, or hepatic progenitor cells has been reported.10,11,32 Furthermore, when HCC cells coexisted in the CoCC and the HCC cells accounted for 10 % or less, the tumor was diagnosed as CoCC.7 However, when the HCC cells accounted for 10 % or more, the tumor was diagnosed as CHC. The gene discussed is MUC1; the disease is hepatocellular carcinoma.