The prostate gland is part of the male reproductive system and is the largest male accessory gland. It typically weighs between 20-40 grams with an average size of 3 x 4 x 2 cm.
The prostate is comprised of 70% glandular tissue and 30% fibromuscular or stromal tissue.
NORMAL ANATOMY
From superior to inferior the prostase is formed:
- The base (just below the urinary bladder).
- The midgland.
- The apex.
It is divided into four histologic zones (fig.
1):
- The peripheral zone represents approximately 70% of the prostate gland.
The PZ is situated on the posterior and lateral side of the prostate and surrounds the distal urethra at the apex of the prostate and extends posterolaterally to the base.
This area is filled by the anterior fibromuscular stroma.
- The central zone represents approximately 25% of the prostate gland tissue and,
lies in the base of the prostate behind the transition zone.
The central zone contains the ejaculatory ducts.
- The transition zone represents approximately 5% of the prostate gland tissue.
It is predominantly anterolateral to proximal urethra and surrounds the prostatic urethra.
The TZ and the periurethral gland tissue are the seat of benign prostatic hyperplasia (BPH).
- Anterior fibromuscular stroma is a non-glandular region which forms the anterior surface of the prostate.
- Base has 6 sectors on each side:
-
- AS: anterior fibromuscular stroma
- TZ: anterior and posterior transition zone
- PZ: anterior and posterior zone
- CZ: central zone around the ejaculatory ducts
- Midportion has 6 sectors on each side:
-
- AS: anterior fibromuscular stroma
- TZ: anterior and posterior transition zone
- PZ: anterior,
posteromedial and posterolateral peripheral zone
- Apex has 6 sectors on each side:
-
- AS: anterior fibromuscular stroma
- TZ: anterior and posterior transition zone
- PZ: anterior,
posteromedial and posterolateral peripheral zone.
PROSTATE CARCINOMA
Prostate carcinoma is the most frequent neoplasm and the sixth leading cause of cancer death in men.
Prostate cancer is usually detected by:
- An elevated prostate-specific antigen (PSA): ≥ 4 ng/dL.
- Abnormal digital rectal examination.
- Clinic: urinary symptoms (nocturia,
hesitancy,
urgency and terminal dribble),
back pain…
95% of prostate cancers are adenocarcinomas which develop from the acini of the prostatic ducts.
70-75% of all prostate cancers originate in the peripheral zone (PZ).
The posterior aspect of this zone can be examined with digital rectal exam.
25% os prostate cancers originate in the transition zone (TZ).
Cancers originating in the central zone (CZ) are uncommon,
and the cancers that occur in the CZ are usually secondary to invasion by PZ tumors.
Prostate cancer can spread by local invasion (typically into the
bladder and seminal vesicles; urethral and rectal involvement are
rare),
lymphatic spread (pelvic nodes first followed by para-aortic
and inguinal nodes), or by haematogenous metastases: bone
(is the most frequent ~90%),
lung,
liver,
pleura and adrenal glands.
Some prostate carcinomas are not life threatening.
It is important to distinguish between carcinomas with and without risk of progression.