Comparison of DNA ploidy in prostatic intraepithelial neoplasia and invasive carcinoma of the prostate: an image cytometric study.

Prostatic intraepithelial neoplasia (PIN) is regarded as the most important premalignant lesion of prostatic epithelium. The aim of this investigation was to find clues to formal pathogenesis of prostatic cancer. For this purpose DNA ploidy (determined by means of image cytometry [ICM] using 4-microns-thick Feulgen-stained paraffin sections) of PIN and invasive carcinoma was compared. Prostatic tissue of 72 patients (mean age, 67.5 years; 82 areas with carcinoma and 71 areas with PIN) was examined. In 44 cases PIN and carcinoma were coexistent in the same prostates, the PIN grade being high in 77% of these cases (P < .05). In higher-grade PIN and higher-grade carcinoma the c-values, 2.5c-exceeding-rate, and aneuploidy rate increased (P < .01). Carcinomas associated with diploid PIN (either low or high grade) showed diploidy and aneuploidy in an equal number of cases, whereas 70% of aneuploid PIN cases (all high grade) were associated with aneuploid invasive carcinomas (P < .01). Conversely, in 71% of the cases with aneuploid carcinoma the coexistent PIN (either low or high grade) was diploid. Our findings show that aneuploidy can be acquired at a preinvasive stage of carcinogenesis in the prostate and suggest that aneuploid high-grade PIN might be regarded as a precursor of some but not all aneuploid prostatic carcinomas. Image cytometry analysis seems to be a promising method for further subclassification of high-grade PIN lesions into groups with putatively lower or higher risk. However, further investigation is necessary to confirm the clinical importance of these results.