Histological changes of the peripheral zone in small and large prostates and possible clinical implications

It is well documented in literature that most prostate carcinomas (PCa) arise in the peripheral zone (PZ). Additionally, an inverse relationship between prostate size and the incidence of PCa has been demonstrated in recent studies. However, little is known about gland distribution in the peripheral zone of larger prostates compared to smaller prostates. In this study, we examined the histo-anatomical gland distribution within the peripheral zone in small and large prostates and discuss possible clinical implications.

A semi-quantitative analysis of gland density and capsule thickness was performed using light microscopy on 10 large (≥80 g) prostate specimens and 10 small (<30 g) prostate specimens from patients who underwent radical prostatectomy at Texas Tech University Health Sciences Center between the years 2010 and 2016. Samples from radical prostatectomies were used to ensure a whole, preserved prostate with an intact surgical capsule. Gland counts were performed on five random fields under 100 × magnification, while capsule thickness was measured on three random fields per case; thus, a total 50 fields and 30 fields were analyzed for each of the two groups for gland counts and capsule thickness measurements, respectively. Microscopy was standardized to the posterior aspect of the prostate, between 4 o'clock and 6 o'clock along the equatorial region between the apex and base.

Large prostates possessed a significantly lower mean gland count per field compared to small prostates (10.34±4.15, n=50 vs 18.00±5.41, n=50; t=8.16, df=49, P<0.001). Additionally, large prostates showed a significantly higher average capsule thickness in millimeters compared to small prostates (1.80 mm, ±1.12 mm, n=30 vs 0.90 mm, ±0.56, n=30; t=8.16, df=49, P<0.001).

The results demonstrate that prostate hypertrophy leads to both decreased gland density in the peripheral zone and increased capsule thickness, suggesting that growth-induced expansion of the prostate against its capsule leads to compression-induced atrophy and fibrosis of glandular tissue within the peripheral zone (PZ). A decrease in gland density within the PZ may have clinical implications shedding light, for instance, on the reduction in PCa incidence in patients with large prostates as compared to smaller prostates, a phenomenon well documented in the literature.