Proliferative Activity of Benign Human Prostate, Prostatic Adenocarcinoma and Seminal Vesicle Evaluated by Thymidine Labeling

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Abstract
The thymidine labeling index (TLI) was measured in vitro in the epithelium and stroma of benign prostate glands and seminal vesicles and in the epithelium of prostatic adenocarcinomas. The mean epithelial TLI of normla peripheral (posterior) prostatic zone was 0.12%, and that of the normal central (deep) zone was 0.11%. Mean normal stromal TLI were 0.08 and 0.06%, respectively. The mean TLI of epithelium in nodular hyperplasia was 0.31%, which differs significantly from normal epithelium (P < 0.05), and the mean stromal TLI was also increased (0.16%, P < 0.1). The mean TLI of prostatic adenocarcinomas was 0.90% (range 0.14-3.90%) which was significantly higher than for either normal epithelium (P < 0.001) or epithelium of nodular hyperplasia (P < 0.05). Trends of increasing TLI with increasing histologic grades and increasing nuclear size and numbers of nucleoli were not significant. The data support participation of both epithelial and stromal proliferation in nodular hyperplasia, and indicate a low basal proliferative rate in normal prostatic glands. The low TLI of prostatic adenocarcinomas relative to other malignancies are consistent with their frequently slowly progressive course. The very low proliferative rate of seminal vesicular epithelium (mean TLI 0.02%) may account for the rarity of seminal vesicular carcinomas.