Immunocytochemical diagnosis of hepatocellular carcinoma and identification of carcinomas of unknown primary metastatic to the liver on fine-needle aspiration cytologies.

Difficulties with cytologic diagnoses on fine-needle aspiration cytology (FNAC) of the liver can be overcome by the application of immunocytochemical panels applied on smears. The aim of the current study was to analyze the performance of a panel of monoclonal antibodies to differentiate hepatocellular carcinoma (HCC) from metastatic carcinoma (MC) or regenerative nodules, and to identify the to date unknown primary sites of carcinomas that had metastasized to the liver. In a validating cohort study, 108 FNACs coin lesions in the liver were routinely evaluated applying immunocytochemistry as an ancillary method. All patients had confirmatory histologic and/or clinical follow-up. A total of 23 HCCs were analyzed for the distinction from MC or regenerative nodules applying a panel of HepPar1, alpha-fetoprotein, BerEP4, CD31, CD68, and Ki-67. A total of 85 cases of unknown primary tumor metastatic to the liver were used to identify the tumor sites applying a panel of CK5/6, CK7, CK20, CA 125, thyroid transcription factor-1 (TTF-1), and Cdx2. Typing accuracy to differentiate HCC from MC or regenerative nodules was 100% and 90.3%, respectively, to identify the primary tumor site of MC. In 23 cases, the site of the primary tumor remained clinically unknown. The application of immunocytochemical panels on the same slide used for microscopic diagnosis is a useful tool in the routine assessment of FNACs of the liver to discriminate HCCs from MC or regenerative nodules and for the identification of primary sites of MC. Their performance should be confirmed in a larger series of cases.