Proliferating cell nuclear antigen immunostaining in breast cancer and its relation to prognosis.

Proliferating cell nuclear antigen (PCNA) appears in the cell nuclei during the late G1 to S phases of the cell cycle and is thought to be closely related to cellular proliferation. The authors have conducted an immunohistochemical study in order to investigate the tissue expression of PCNA and its clinical significance in breast cancer. Excluding cases with absolutely no positive cells on the section specimen, the mean value (%) for the PCNA labeling index (LI) was 30.4 in 187 cases of invasive ductal carcinoma. No correlations between PCNA LI and any clinicopathological factors such as tumor diameter and tumor stage were observed. Also, no significant correlation was observed with Ki-67 LI. A positive correlation was, however, observed with the tissue expression of c-erbB-2 protein. We divided 82 patients with stage II invasive ductal carcinoma into PCNA LI of < 10, PCNA LI of 10-50 and PCNA of > 50, and analyzed the specimens for any correlation with prognosis. The group with PCNA LI of > 50 had significantly poorer prognoses than the other groups. From the above, we concluded immunostaining for PCNA to be useful as a prognostic factor and as an indicator of the degree of malignancy in breast cancer.