Prostatic intraepithelial neoplasia and invasive carcinoma in total prostatectomy specimens: distribution, volumes and DNA ploidy.

Prostatic intraepithelial neoplasia (PIN) has been postulated to be the main precursor of invasive carcinoma of the prostate (IC). The occurrence, distribution and volumes of PIN and IC in addition to grade were studied in 54 patients who underwent total prostatectomy because of localised IC (T0d-T2 NO MO). PIN always occurred multifocally, localised generally in the peripheral zone (PZ) and was found in all cases. PIN 1 was the most common grade, PIN 3 the least. PIN 3 occurred exclusively in the PZ, in the vicinity of or intermingled with high grade IC. PIN and IC grades were usually concordant. The relative volumes of IC and PIN showed an inverse relationship, i.e. at small IC + PIN volumes PIN dominated, whereas at large IC + PIN volumes both relative and absolute PIN volumes were lower. Furthermore, with increasing PIN grade a tendency towards an increase in tumour volume, Gleason score and frequency of disruption of the basal cell layer was observed. These findings indicate progression from PIN to IC. DNA ploidy of PIN areas was determined by means of flow cytometry. Areas containing PIN 1, 2 or 3 were sampled (1 plug/ml of PIN). All foci displayed only diploid DNA profiles regardless of PIN volume and grade, even with coexistent IC displaying heterogeneous DNA patterns. Our results support the claim that low and medium grade prostatic carcinoma arises from near-diploid PIN stemlines and may progress into heterogeneous tumours containing non-diploid stemlines.