A portion of the prostate gland in shown in this low-magnification micrograph. A small section of the capsule (Cap) of the gland is seen in the upper left corner. The rest of the field is filled with the glandular and stromal components of the prostate. The secretory tubuloalveoli of the prostate gland vary greatly in form, as is evident in the figure. They may appear as tubes, as isolated alveoli, as alveoli with branches, or as tubes with branches. Tangential sections through alveoli may even produce the appearance of “epithelial islands” (arrowheads) in the lumen of the alveoli.
This is due to the extremely uneven contour of the epithelial surface. It should also be noted that many of the alveoli may appear rudimentary in structure (arrows). These are simply in an inactive state and are increasingly observed in older individuals. As noted above, aggregations of dead epithelial cells and precipitated secretions form prostatic concretions (C) in the lumina of the alveoli; these gradually increase in number and size with age. The concretions stain with eosin and may have a concentric lamellar appearance, as is clearly shown in the concretion in the lower right. With time, they may become impregnated with calcium salts and thus be easily recognized in X-rays of the lower abdomen.
Glands and fbromuscular stroma, prostate, human, H&E 178; upper inset 350; lower inset 650.
In this higher magnification view of a portion of the prostate gland, the fbromuscular stroma is clearly seen both immediately subtending the secretory epithelium of the tubuloalveoli as well as in deeper, nonsecretory areas. In the upper inset, corresponding to the larger rectangle, the intensity of the staining of the smooth muscle (SM) clearly distinguishes it from the fibrous stromal connective tissue with which it is intimately intermingled. There are no clearly outlined bundles or layers of smooth muscle in the prostate; rather, it is randomly arrayed throughout the stroma. Prostatic concretions (C) are again evident in the lumina of alveoli, in one instance compressing the epithelium to a degree that makes it nearly unrecognizable. The lower inset, corresponding to the smaller rectangle, clearly demonstrates the pseudostratified columnar nature of the prostatic epithelium (Ep). Well-delineated basal cells (arrowheads) are seen along with the taller columnar secretory cells. A small blood vessel immediately subtending the epithelium is recognizable by the red blood cells in its lumen. A lymphocytic infiltration appears to fill the stroma along the lower border of this image suggesting an inflammatory process  occurring in the prostate gland.
PLATE 90 KEY BV, blood vessel C, prostatic concretion Cap, capsule Ep, epithelium L, lymphocytes SM, smooth muscle arrows, inactive alveoli arrowheads: top fgure, “epithelial islands”; bottom figure, basal cells