Canalicular immunostaining of neprilysin (CD10) as a diagnostic marker for hepatocellular carcinomas

Neprilysin (CD 10) is expressed in both normal and neoplastic liver tissue, where it exhibits a characteristic canalicular pattern (CD10(can)) similar to the one observed when antibodies cross-react with biliary glycoprotein I (p-CEA). The aim of this retrospective study was to investigate the use of CD10(can) in differentiating between hepatocellular carcinomas (HCCs; 63 specimens) and nonhepatocellular carcinomas (non-HCCs) metastatic to the liver (non-HCC; 25 specimens). Immunostaining was performed with antibodies directed against CD10, p-CEA, and a-fetoprotein (AFP). Albumin mRNA was detected by nonradioactive in situ hybridization (ISHalbumin). In the HCC group a canalicular staining pattern for CD10 was found in 43 (68.3%) specimens, AFP was found in 15 (23.8%) specimens, and a canalicular staining pattern for p-CEA was present in 60 (95.2%) specimens. ISH albumin was performed in 35 HCC specimens and showed labeling of tumor cells in 3 (85.7%) specimens. In the non-HCC group CD10(can), and p-CEA, immunostaining for AFP and labeling for ISH albumin were confined to non-neoplastic liver tissue. Sensitivity and specificity were, respectively, 68.3% and 100% for CD10(can), 23.8% and 100% for AFP, 95.2% and 100% for canalicular p-CEA, and 86.4% and 100% for ISHalbumin. Our results demonstrate that canalicular staining for CD10 is a highly specific marker of hepatocytic differentiation. Although it does not differentiate between benign and malignant lesions, CD10(can) is clearly useful in differentiating between HCC and non-HCC.