Immunohistochemical Expression Analysis of EpCAM in Hepatoblastomas

The epithelial cell adhesion molecule (EpCAM) is involved in oncogenesis of hepatoblastomas (HBs). Prior genomic profiling studies showed higher EpCAM expression and worse prognosis in HBs containing primitive histotypes, however, this has not been fully addressed from an immunohistochemical perspective. Our goal is to characterize differential EpCAM immunohistochemistry (EpCAM-IHC) among HBs histotypes. We retrieved 62 HBs from 52 patients. EpCAM-IHC was performed (anti-MOC-31, 1:50 dilution; Cell Marque Corporation, Rocklin, CA) and graded in histotypes using the immunoreactive score. The median age of patients was 2 years (range: 0.4 to 9 y) with a M:F ratio of 1.9. Outcome information was available in 38 patients (alive=30, alive with disease=3, and deceased=5) with median follow-up of 60 months (range: 2 to 171 mo). EpCAM-IHC showed notable overexpression (immunoreactive score >4) in embryonal (89%) and crowded fetal (74%) in contrast to glandular (33%), well-differentiated fetal (32%), and small cell undifferentiated/blastemal (3%) components. Mesenchymal elements were negative. In summary, EpCAM-IHC is helpful to distinguish between epithelial components as it is progressively lost in the transition from embryonal to crowded fetal and into well-differentiated fetal histotypes. Its preferential expression among primitive HBs might have therapeutic and prognostic implications. The significance of its largely negative expression in small cell undifferentiated/blastema is interesting despite its presumed immaturity, deserving further studies.