Prostate cancer

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Prostate cancer is the most common cause of cancer and the second most common cause of cancer deaths in men in the United States.
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 prostate.
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 biopsy.

Sonography :
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 zones (10%).
Most commonly, cancers are imaged by TRUS as hypoechoic masses (70%) although cancers may be isoechoic (10-20%) or, very rarely, hyperechoic.
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.

DIFFERENTIAL DIAGNOSIS
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).

Reference :
* 1 : Karakiewicz PI, Perrotte P, McCormack M, Peloquin F, Perreault JP, Arjane P, Widmer H, Saad F. Early detection of prostate cancer with ultrasound-guided systematic needle biopsy. Can J Urol. 2005 Jun;12 Suppl 2:5-8.
* 2 : Rosi P, Lilli P, Tascini MC, Di Lisa M, Gilardi R, Mearini L, Porena M. Echocolor and power Doppler in prostate carcinoma. Does a diagnostic pattern really exist? Arch Ital Urol Androl. 2005 Mar;77(1):47-9.
* 3 : Tang J, Li X, Wang N, Zhang S, Lin Q, Li J, Shi H. Correlation between hypoechoic nodules on ultrasonography and benign hyperplasia in the prostatic outer gland. J Ultrasound Med. 2005 Apr;24(4):483-8.
* 4 : Clements R: Contemporary ultrasound guided biopsy in the diagnosis of prostate cancer. Imaging 2001; 13: 18-26.
* 5 :Halpern EJ, Rosenberg M, Gomella LG: Prostate cancer: contrast-enhanced us for detection. Radiology 2001 Apr; 219(1): 219-25
* 6 : Lavoipierre AM, Snow RM, Frydenberg M, et al: Prostatic cancer: role of color Doppler imaging in transrectal sonography. AJR Am J Roentgenol 1998 Jul; 171(1): 205-10
* 7 :Ukimura O, Troncoso P, Ramirez EI, Babaian RJ: Prostate cancer staging: correlation between ultrasound determined tumor contact length and pathologically confirmed extraprostatic extension. J Urol 1998 Apr; 159(4): 1251-9