Proliferating cell nuclear antigen (PCNA) and pediatric tumors: assessment of proliferative activity

Monoclonal antibodies to proliferating cell nuclear antigen (PCNA) were used to detect proliferating cells in pediatric tumors fixed in Carnoy's solution. The percentage of staining cells was quantified using image analysis and compared to the S + G2M phase fraction as determined by flow cytometry. Although there was a general correlation between these indices of cellular proliferation, some variation was noted between tumor systems as well as within a specific tumor type. In some cases this variation was easily explicable by the morphologic findings (e.g., tumor heterogeneity and sampling differences, stromal cell proliferation, necrosis, extramedullary hematopoiesis), whereas in others it appeared to be an intrinsic property of the cell line. It is concluded that PCNA immunostaining is a useful and reproducible method of assessing one aspect of cellular proliferative activity and especially of addressing the questions, "which cells are dividing and where?" It has some advantages over flow cytometry in that it maintains tissue integrity and morphologic relationships.