pCEA Canalicular Immunostaining in Fine Needle Aspiration Biopsy Diagnosis of Hepatocellular Carcinoma

To assess the usefulness of bile canalicular polyclonal carcinoembryonic antigen (pCEA) immunostaining in fine needle aspiration biopsy (FNAB) diagnosis of hepatocellular carcinoma (HCC). Hepatic FNAB with cell blocks of 72 confirmed and 6 possible HCC and 23 non-HCC malignancies (controls) were analyzed. Sections were stained with antibody to pCEA using the streptavidin biotin-immunoperoxidase method and results correlated with tumor grade and other parameters used in HCC diagnosis. Canalicular pCEA staining was observed in 60 (83%) of the 72 HCC. This category comprised 29%, 31%, 36% and 4% grade 1-4 tumors, including 7 small cell, 4 clear cell and 1 giant cell variants. With increasing anaplasia, the canaliculi became infrequent, irregularly distributed, and increasingly distorted and interrupted. Canalicular staining helped distinguish clear and small cell variants from metastatic renal cell carcinomas and neuroendocrine tumors, respectively. Of the six problematic cases, one was confirmed to be HCC with plasmacytoid features and five to be adenocarcinomas, of which three could have been combined hepatocellular-cholangiocarcinomas. Liver cell dysplasia also displayed an abnormal canalicular pattern. No cytoplasmic staining was seen in pure HCC. pCEA immunostaining cannot separate malignant, dysplastic or benign hepatocytes. It is usually not required in cytodiagnosis of most HCC. However, it is most helpful in confirming atypical variants of HCC, which may mimic other tumors.