Intratumor variation in cell proliferation in breast carcinoma as determined by antiproliferating cell nuclear antigen monoclonal antibody and automated image analysis.

Immunohistochemical detection of the proliferating cell nuclear antigen (PCNA) represents a potentially useful tool for the study of tumor proliferative activity. To study the intratumor heterogeneity of tumor growth, 88 breast carcinomas were immunostained with the anti-PCNA antibody 19F4 and analyzed with the CAS 200 image analysis system (Cell Analysis System, Inc., Lombard, IL). For each sample, 12 fields from both the central and the peripheral areas of the tumor were measured. The proportion of PCNA-positive nuclear area in the whole tumor (PCNAt score) varied from 0.7% to 45.2% (median, 14.4%). There was considerable intratumor heterogeneity in the staining for PCNA. In 79% of the specimens, the PCNA score was higher in peripheral areas than in the center of the tumor, the average difference being +3.4% (range, -9.2- +15.1%; P < 0.0001, Student's t-test). The S-phase fraction, determined by DNA flow cytometry of the same tumors, varied from 2.0% to 32.6% (median, 10.0%). The PCNA score showed a significant correlation with the S-phase fraction (r = 0.469, P < 0.001). Most divergent results were those with high PCNA scores and low S-phase fraction; possible explanations for this are discussed. The PCNA score also was related to the histologic grade of the tumors (P = 0.03, analysis of variance). In conclusion, proliferation indices obtained from different areas of a tumor can differ significantly because of intratumor heterogeneity in growth fractions. The PCNA immunostaining correlates with well-known prognostic factors (S-phase fraction and histologic tumor grade) in breast carcinoma.