Mills Ch35 Prostate

972

SECTION IX : GenitourinaryTract

posterior surface rests directly against the muscle of the rectal wall (24). The capsule is typically fused to the fascia with occasional remnants of an interposed adipose layer. In the adult, there remain only scattered microscopic islands of fat along with a variable number of smooth muscle fibers. Superiorly (toward the base), Denonvilliers’ fascia extends above the prostate to cover the posterior sur- face of the seminal vesicles in a loosely adherent fashion (Fig. 35.17). Laterally, the fascia leaves the posterior cap- sule where the prostate surface begins to deviate anteriorly, and it continues in a coronal plane to anchor against the pelvic sidewalls. Thus, the prostate and seminal vesicles are suspended along the anterior aspect of this fascial mem- brane in a similar fashion to the uterus being suspended from the broad ligament in the female. As the seminal vesicles leave the prostate base, they extend laterally along its basal surface. Often there is no capsule between the two organs, at least for the medial cen- timeter or more of the seminal vesicle. The degree of fusion between the two muscular walls is variable between pros- tates, but there is frequently no boundary between the two organs medially with a minimal amount of common muscu- lar wall separating the most basal central zone gland lumen from the seminal vesicle lumen (Figs. 35.18 and 35.19). Where Denonvilliers’ fascia separates from the prostate capsule posterolaterally, the space between them is filled with adipose tissue in a thick layer between the anterior aspect of the fascia and the posterolateral capsular surface of the prostate. The autonomic nerves, from the pelvic plexus to the seminal vesicles, prostate, and corpora cavernosa of the penis, travel in this fatty layer. The nerves, along with the blood vessels to the prostate, originate from bilateral FIGURE 35.18  Parasagittal section of prostate base located almost at midline. Bladder neck smooth muscle above the level of bladder neck lumen is seen as a small dark patch ( B ) at far right. A layer of fat ( F ) cov- ers the dome-shaped surface of the anterior central zone ( top center ). All glandular tissues within is central zone. One main duct ( center ) is seen in profile as it flares out toward the base, generating elaborate acinar struc- tures. Behind the seminal vesicle ( SV ), the posterior central zone extends superiorly as a narrow plate. Denonvilliers’ fascia ( D ) is not adherent behind the seminal vesicles but blends with the capsule below.

FIGURE 35.19  Minimal muscular tissue separating the prostatic central zone ( right ) from the seminal vesicles ( left ) at the base of the prostate.

neurovascular bundles that course vertically along the pelvic sidewalls (Fig. 35.17) (25). Most of the nerve branches to the prostate leave the neurovascular bundle just superior to the prostate base and course medially as the superior pedi- cle. These nerve branches fan out to penetrate the “superior pedicle insertion area” of the capsule, centered at the pos- terolateral aspect of the prostate base (25,26) and extend as far as mid gland. Some nerve trunks travel medially across the prostate base, sending branches into the central zone, but the majority of nerve branches fan out distally and pen- etrate the capsule at an oblique angle. Small microscopic paraganglia may also be seen in association with extrapros- tatic nerves and ganglia, reportedly identified in up to 8% of radical prostatectomies (27). They are characterized by small collections of round cells with clear or amphophilic cyto- plasm, often with small cytoplasmic granules and an associ- ated small capillary vasculature (Fig. 35.20). Some variable

FIGURE 35.20  While paraganglia may be seen in extraprostatic tis- sues, often in association with peripheral nerves and ganglia, very rare examples may be intraprostatic.