PCNA immunostaining in breast cancer.

Expression of proliferating cell nuclear antigen (PCNA) has been shown to be of prognostic value in patients with certain types of cancer. The aim of this study was to determine if the abundance of PCNA is inversely correlated with survival of patients with breast cancer. Paraffin blocks were available from 68 patients, all of whom had been followed clinically for at least 5 years. Sections from 20 patients showed no reactivity to PCNA and were excluded from the study because it was not possible to distinguish between true negatives and false negatives (those due to poor fixation of the original specimens). The PCNA index (the number of stained cancer cells as a percentage of the total number of cancer cells present) was calculated for the remaining 48 patients. Results were analysed by Wilcoxon's rank sum test (two tailed) and Pearson's correlation coefficient. There was no statistical difference between the PCNA indices of those patients dead from their disease within 5 years of diagnosis compared with those alive and without signs of breast cancer at 5 years. There was also no correlation between PCNA index and size of the cancer, involvement of axillary lymph nodes, time to recurrence or time to death. There was, however, a significant correlation between PCNA index and histological grade (P = 0.029). It appears that PCNA staining of stored paraffin sections is of little prognostic value in patients with breast cancer.