There are few previous studies in the literature evaluating cell proliferation and this may be explained by the complex nature of this neoplasm and its heterogeneous cell com-position.10 It has already been described that, in HD, HRS cells express proliferating cell nuclear antigen (PCNA) and p53 in more than 50% of the cases and that these expressions may play a role in the pathogenesis of the disease.11 PCNA is a cell cycle-associated protein that interferes with cell proliferation in normal and tumor cells. This evidence concerns the gene PCNA and neoplasm.