Content Reviewers:Rishi Desai, MD, MPH
The prostate gland is a large and dense exocrine gland that’s responsible for secreting a white alkaline fluid that makes up about 30 to 50 percent of the seminal fluid volume.
It’s the largest accessory sex gland in the male reproductive system, measuring approximately 3 cm in length and width, and a height of 5 cm.
The average weight of a normal prostate gland is about 11 grams.
Due to its similar size and shape, it’s sometimes compared to a walnut.
The gland surrounds the most proximal portion of the urethra or prostatic urethra, just below the bladder and consists of 30 to 50 branched tubuloalveolar glands, such as the ones seen in this low power image of the prostate.
The glands all drain into converging ducts that eventually empty into the prostatic urethra.
The alkaline fluid that’s secreted by the prostate gland also includes various small molecules, fibrinolysin, citric acid, and the clinically important prostatic acid phosphatase or PAP, and prostate-specific antigen or PSA.
Normally, only a small amount of PSA will leak into the prostate’s vasculature and circulate in an individual’s blood.
Because of this association, a PSA serum level is often used as a tumor marker for prostate cancer.
PSA and PAP immunostains can also be used on tissue samples to assist with the diagnosis of prostate cancer, such as this section from a lymph node, where a PSA stain is highlighting a metastatic prostate adenocarcinoma in brown.
Similar to this image at 40x magnification, the prostate will have glandular structures called acini that are surrounded by supporting fibromuscular stroma.
Each acinus has two layers of cells: an epithelial layer and a basal layer.
The glandular epithelial cells can become hyperplastic and consist mostly of simple columnar and cuboidal cells, with some regions having pseudostratified columnar epithelium.
The basal layer consists of smaller stem cells that rest on the basement membrane.
The basal layer will not be seen in prostatic carcinoma.
There are also neuroendocrine cells present, but they aren’t easily identified with an H&E stain.
With age, the acini have a higher probability of accumulating thick secretions that form hyaline spherical masses or concretions, called corpora amylacea, which can be seen in these three alveoli.
They can vary in size, but typically have layered or lamellated bodies that can be seen under the microscope.
Over time, they may become partially calcified as well.
The corpora amylacea are normal findings in the prostate and can be seen in normal lung tissue as well.