Prostatic basal cells in the peripheral and transitional zones: zonal variation in morphology and in immunophenotype.

Background: Benign prostatic hyperplasia and prostatic adenocarcinoma exhibit prominent zonal predilections. Basal cells from the transitional zone and from the peripheral zone are postulated to have different underlying biological properties. We studied basal cells in both prostatic zones.
Methods: Tissue microarrays (TMA) were prepared from 65 whole-mounted prostatectomy specimens with prostatic adenocarcinoma. The transitional zone and peripheral zone were sampled from each prostate. TMA sections were stained with a basal cell cocktail (CK 34betaE12 + p63). The immunostaining pattern and the morphology of basal cells were recorded.
Results: Triangular-shaped basal cells were highlighted by CK 34betaE12 cytoplasmic and p63 nuclear staining. These basal cells had their long axis oriented perpendicular to the basement membrane and their apex toward the lumen interdigited between secretory luminal cells. This morphology was seen in the majority of peripheral zone benign prostatic glands (92.0%) but only a minority of transitional zone benign prostatic glands (18.0%). Basal cells of the transitional zone showed weak or absent CK 34betaE12 staining in 65.9% of glands while maintaining p63. All glands with high-grade prostatic intraepithelial neoplasia (HGPIN) contained the triangular basal cells. In addition, basal cell clusters were identified in 8.7% of peripheral zone glands and 5.2% of HGPIN glands.
Conclusions: Our results indicate that the basal cell morphology and the basal cell immunophenotype have a zonal variation. The finding of a unique morphology of basal cells and the presence of basal cell clusters in the peripheral zone suggests that the peripheral zone might be the stem/progenitor cell-rich area in the human prostates.