prostate needle biopsy
Wednesday 8 February 2012
The current standard method for detection of prostate cancer is by transrectal ultrasound-guided core biopsies.
Directed biopsies to either lesions detected on digital rectal examination or on ultrasound should be combined with systematic biopsies taken according to a standardized protocol.
The sextant protocol samples the apex, mid and base region
bilaterally. Sextant biopsies aim at the centre of each half of the prostate equidistant from the midline and the lateral edge while the most common location of prostate cancer is in the dorsolateral region of the prostate.
Several modifications of the sextant protocol have been proposed. Recent studies have shown that protocols with 10 to 13 systematic biopsies have a cancer detection rate up to 35% superior to the traditional sextant protocol.
This increased yield relates to the addition of biopsies sampling the more lateral part of the peripheral zone, where a significant number of cancers are located.
Approximately 15-22% of prostate cancers arise in the transition zone, while sextant biopsies mainly sample the peripheral zone. Most studies have found few additional cancers by adding transition zone biopsies to the sextant protocol (1.8-4.3% of all cancers detected) and transition zone biopsies are usually not taken in the initial biopsy session.
Handling of needle biopsies
Prostate biopsies from different regions of the gland should be identified separately. If two cores are taken from the same region, they can be placed into the same block. However, blocking more than two biopsy specimens together increases the loss of tissue at sectioning.
When atypia suspicious for cancer is found, a repeat biopsy should concentrate on the initial atypical site in addition to sampling the rest of the prostate.
This cannot be performed unless biopsies have been specifically designated as to their location.
The normal histology of the prostate and its adjacent structures differs between base and apex and knowledge about biopsy location is helpful for the pathologist. The location and extent of cancer may be critical for the clinician when selecting treatment option.
The most common fixative used for needle biopsies is formalin, although alternative fixatives, which enhance nuclear details are also in use.
A potential problem with these alternative fixatives is that lesions such as high-grade prostatic intraepithelial neoplasia may be over-diagnosed.
Immunohistochemistry for high molecular weight cytokeratins provides considerable help in decreasing the number of inconclusive cases from 6-2%.
It has therefore been suggested that intervening unstained sections suitable for immunohistochemistry are retained in case immunohistochemistry would be necessary. Intervening slides are critical to establish a conclusive diagnosis in 2.8% of prostate biopsies, hence, sparing a repeat biopsy.
Handling and Pathology Reporting of Prostate Biopsies, Eur Urol, 2004.
Should intervening benign tissue be included in the measurement of discontinuous foci of cancer on prostate needle biopsy? Correlation with radical prostatectomy findings. Karram S, Trock BJ, Netto GJ, Epstein JI. Am J Surg Pathol. 2011 Sep;35(9):1351-5. PMID: 21836493
The value of mandatory second opinion pathology review of prostate needle biopsy interpretation before radical prostatectomy. Brimo F, Schultz L, Epstein JI. J Urol. 2010 Jul;184(1):126-30. PMID: 20478583