An immunohistochemical analysis of 13 cases with combined hepatocellular and cholangiocellular carcinoma

Thirteen cases of combined hepatocellular (HCC) and cholangiocellular carcinoma (CCC) were examined. In addition to routine pathology, immunoreactivities for carcinoembryonic antigen, α‐fetoprotein (AFP), cytokeratin (Cam 5.2 and AE1), epithelial membrane antigen (EMA) and tumor‐associated glycoprotein 72 (B72.3) were also examined. The average age of the 13 cases was 64.8 years, which lay between the average ages of pure HCC and CCC cases. They were categorized as separate type (2), collision type (6), and intermingled type (5). AE1 and EMA were the best markers to differentiate the CCC from the HCC area. B72.3 immunoreactivity was detected only in CCC (46%). There were no transitional features between HCC and CCC in two cases of the separate type and two cases of the collision type. However, focal transitional features from HCC to CCC were observed in all cases of the intermingled type and in four of six cases of the collision type. In one case of the intermingled type, many cancer cells contained both bile and mucus simultaneously, and revealed dual immunoreactivities. The conclusions are: 1) the combined type is generated from two sources; one is the intrahepatic double cancer (thoroughly separate type and a part of the collision type) and another is the stem cell origin with diverse phenotypes (intermingled type and a part of the collision tumor); and 2) AE1 was the most helpful marker to differentiate the CCC area from HCC, and other markers, e.g. AFP for HCC and EMA, CEA, and B72.3 for CCC, were also supportive but somewhat limited in the differential diagnosis.