Prostate cancer is the most common cause of cancer
and the second most common cause of cancer deaths in men in the
Approximately 95% of prostate cancers are adenocarcinomas developing
in the acini of prostatic ducts.
Prostatic carcinoma generally is slowly progressive and may cause
no symptoms. With the development of prostatic ultrasonographic
technology, urologists have gained a tool that allows better visualization,
more accurate biopsy and earlier detection of carcinoma of the
Carcinoma of the prostate should be suspected on the basis of
abnormal digital rectal findings, hypoechoic lesions on TRUS,
or elevated levels of PSA. However, diagnosis requires histologic
confirmation, most commonly by TRUS-guided transrectal needle
TRUS plays a central role in the contemporary diagnosis of prostate
cancer. Using TRUS, the prostate is shown to be divided into an
outer gland (PZ and CZ) and an inner gland (TZ).
Based on McNeal's histologic studies, the prostate is composed
of glandular elements (2/3 volume) and nonglandular tissue or
fibromuscular stroma (1/3 volume). The glandular tissue may be
subdivided into a peripheral and central glands. The peripheral
gland is further subdivided into the peripheral and central zones.
The central or inner gland is composed of transitional zone and
peri-urethral glandular tissue. Cancer arises most frequently
from the peripheral zone (70%), transition zone (20%), and central
Most commonly, cancers are imaged by TRUS as hypoechoic masses
(70%) although cancers may be isoechoic (10-20%) or, very rarely,
Most prostatic carcinomas (75 %) will show on ultrasound but isoechoic
tumors may be missed on gray scale ultrasound. the addition of
color flow Doppler can identify another 15 pet cent. Isoechoic
lesions may be identified with a capsular bulge or distortion.
investigators have used color Doppler to demonstrate increased
flow within the tumor mass as a means of distinguishing a benign
process from a malignant one. Unfortunately, increased flow may
be seen with benign entities such as infection. Both prostate
cancer and prostatitis may have increased vascularity, as shown
on color and power Doppler sonograms.
Tumor extension into the capsule, periprostatic lymph nodes, seminal
vesicles, or surrounding tissues may be shown sonographically.
If lymph nodes are detected, tumor extension should be suspected.
The normal seminal vesicles tend to be moderate in echogenicity.
Involvement of cancer can be suspected with asymmetry between
the two. The seminal vesicles are normally fluid-filled structures.
With tumor infiltration, this can change to a more solid composition.
The criteria for determination of subtle seminal vesicle involvement
is the obliteration of the "nipple" sign. Asymmetric erosion of
the "nipple" has been determined to be a relatively reliable sign
of tumor infiltration. This is not a consistent finding, and thus
its absence may be inconclusive. Another highly reliable sign
of seminal vesicle tumor infiltration : it is the opening or the
obliteration of the vesico-prostatic angle.
TRUS may be used for local staging of prostate cancer because
it can demonstrate bulges of the prostate capsular outline or
overt extracapsular extension.
Sonography may follow up these tumors, therapy usually results
in an increase in parenchyma echogenicity.
Many pathologic processes can appear as a hypoechoic area or as
a hypervascular area on color or power Doppler sonograms. The
differential diagnoses of a hypoechoic area include :
* Benign prostatic hyperplasia.
* Focal prostatis.
* granulomatous prostatitis
* Tuberculosis. * Prostatic abscess.
* prostatic atrophy and infarction
* Focal amyloid deposition.
* Muscle around ejaculatory duct
* Dysplastic lesions and pre-invasive stage of some prostate cancers
prostatic intraepithelial neoplasia (PIN).
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