AIMS: To investigate the staining patterns of CD10 in hepatocellular carcinoma (HCC), focal nodular hyperplasia (FNH), and intrahepatic cholangiocarcinoma (ICC). METHODS: The expression pattern of CD10 was analyzed using immunohistochemistry in HCC cases. Focal nodular hyperplasia (FNH) and intrahepatic cholangiocarcinoma (ICC) cases were also examined. CD10 staining pattern in relationship with histologic subtypes and growth patterns of HCC was also analyzed. RESULTS: CD10 expression was observed in 61% (64/105) of HCC cases, 100% (12/12) of FNH cases, and 31.6% (6/19) of ICC cases. Different expression patterns were noted, including cell membrane (13/64
20.3%), luminal (9/64
14.0%), cytoplasmic puncta (15/64
23.4%), and canalicular (27/64
42.3%) patterns of CD10 expression in HCC. Interestingly, CD10 membranous expression was found to be associated with steatosis changes. The observed pattern rates of CD10-positive ICC cases were 16.6% (1/6) for cell membrane, 50% (3/6) for cytoplasmic, and 33.3% (2/6) for luminal patterns
with 2 samples having a 1+ score (33.3%), 1 having a 2+ score (16.7%), and 3 having a 3+ score (50%). CONCLUSIONS: Different CD10 expression patterns were observed in HCC, FNH, and ICC. A canalicular CD10 expression pattern does not distinguish between benign and malignant lesions in the HCC, but reduced CD10 expression or no canalicular pattern suggests that a tumor is more likely to be HCC. Contrary to previous understanding, we found that CD10 is also expressed in ICC cases.