MOC-31 aids in the differentiation of metastatic adenocarcinoma from hepatocellular carcinoma

BACKGROUND. Fine-needle aspiration biopsy (FNAB) is frequently used to diag nose mass lesions in the liver. Differentiating metastatic adenocarcinoma f rom primary hepatocellular carcinoma can be difficult. Despite a number of morphologic criteria, there remain occasional cases in which the cytologic features fail to resolve this differential reliably; in these cases ancilla ry studies may be useful. Recently, it has been reported that the antibody MOC-31 reliably separates metastatic adenocarcinoma from hepatocellular car cinoma. In this study we examine the utility of MOC-31 in liver FNAB materi al. METHODS. Thirty-three archival, alcohol-fixed, paraffin-embedded cell block s rep resenting 17 cases of hepatocellular carcinomas and 16 cases of metas tatic ade nocarcinoma were retrieved. After protease digestion, the section s were immunostained with the antibody MOC-31 (Dako, Carpinteria, CA) utili zing a modified avidin-biotin complex technique. Only membrane-based reacti vity was considered positive. RESULTS. In five cases there was insufficient diagnostic material remaining in the cell block for immunohistochemical staining. Among the remaining ca ses, MOC-31 reactivity was observed in 10 of 12 metastatic adenocarcinomas and 2 of 16 hepatocellular carcinomas. For metastatic adenocarcinoma the pr esence of MOC-31 reactivity yields a sensitivity of 83%, a specificity of 8 7%, a positive predictive value of 83%, and a negative predictive value of 87%. CONCLUSIONS. MOC-31 is useful in separating metastatic adenocarcinoma from hepatocellular carcinoma in FNAB cell block material. Cancer (Cancer Cytopa thol) 1999;87:295-8. (C) 1999 American Cancer Society.