Monoclonal Antibody KI-67 Defined Growth Fraction in Benign Prostatic Hyperplasia and Prostatic Cancer

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Abstract
Growth fractions were assessed immunohistochemically in prostatic tissues with benign glandular hyperplasia (BPH) and in specimens of prostatic cancer using the monoclonal antibody Ki-67. This antibody is specific for a proliferation-associated nuclear antigen. In BPH tissues about 0.3% of nuclei of epithelial cells was reactive with Ki-67. The Ki-67 positive nuclei were distributed equally among the basal and luminal cells of the hyperplastic prostatic acini. In prostatic cancer the Ki-67 defined growth fraction ranged from 0.4% to 9.1% (mean value 2.9%). Cancers with a cribriform growth pattern and tumors composed of solid areas of undifferentiated cancer cells showed the highest growth fraction (average values 4.0%, respectively 7.6%). The investigated four tumors composed of undifferentiated solitary tumor cells with diffuse infiltration of the stroma demonstrated an unexpectedly low growth activity (average 1.2%). In cancers with a glandular growth pattern the Ki-67 defined growth fraction of tumor cells varied from 2.2% to 5%. Compared with other epithelial tumors these values are low, but they are in agreement with the earlier findings on prostatic cancer obtained with 3H-thymidine labeling and bromodeoxyuridine incorporation. The observed variation in the level of Ki-67 defined growth activity partly related to the histological tumor pattern suggests that Ki-67 labeling may serve as a prognostic factor additional to the current histopathological grading criteria of prostatic cancer.