How Much Tissue Sampling Is Required When Unsuspected Minimal Prostate Carcinoma Is Identified On Transurethral Resection?

Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology
Article Date: 02 Sep 2008 - 1:00 PDT

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UroToday.com - Transurethral resection of prostate (TURP) is still a common urological procedure that is primarily used in the current practice for the surgical management of benign prostatic hyperplasia. The quantity of tissue chips received in the pathology laboratory for examination varies. Recommendations by the College of American Pathologists (CAP) require submission of specimens weighing 12 grams or less in their entirety, usually in 6 to 8 cassettes. For specimens greater than 12 grams, the initial 12 grams should be submitted, and one cassette for every additional 5 g may be submitted. The CAP committee recently added a recommendation that "if an unsuspected carcinoma is found in the tissue submitted and it involves 5% or less of the tissue examined, the remaining tissue is generally submitted for microscopic examination". Accurate patient staging is important clinically because patients with incidental tumors found on histology involving 5% or less of resected tissue (stageT1a), require no further invasive treatment, particularly in patients older than 60 years. In contrast, patients with T1b tumours, that involve more than 5% of the resected tissue, are considered at much higher risk for disease progression (33% in one study) and usually require an additional treatment.

In this study, we questioned whether there is a need for additional sampling, when incidental minimal carcinoma involving 5% or less of the tissue is detected in the initial TURP specimen in the contemporary practice. In our study, we initially submitted 6 cassettes/blocks (median 1.7g/block) for all TURP specimens, which would approximate 10-12g of tissue. This approach provided a high probability that most T1a and all T1b cancers would be diagnosed in the initial examination. Our aim was to investigate the yield of additional tissue sampling only when T1a disease is encountered. We have restricted our study to stage pT1a, and not pT1b tumors, since previous studies have shown that downstage would not occur in patients with T1b tumors if additional tissue is sampled.

This prospective study, conducted in a large centralized uropathology practice demonstrated that the initial random sample of 6 cassettes/blocks was sufficient to accurately identify the Gleason score and the tumor volume in the entire resected TURP tissue specimen, which ranged from 10-125 g. Although tumors were found in the additional partial and complete samples in 73% (19/26) of cases, additionally detected tumor volumes did not alter the stage from T1a to T1b in any of the cases. Subsequent partial and complete sampling had no additional yield over the initial 6 cassettes/ blocks in establishing correctly the final T1 substage and the Gleason score. Our study also did not identify a significant tumor volume variation in the additional partial and complete samples, which indicates that tumor foci are distributed uniformly in the sampled chips. In all studied cases, regardless of the patient age and weight of the specimen, Gleason score and overall tumor percentage remained unchanged. For quality assurance, partial sampling of 1 block for 5g of the residual tissue should be considered a reasonable option when unsuspected carcinoma is found and it involves 5% or less of the tissue examined in the initial TURP specimen.

According to our study, this approach should be adequate, regardless of the patient age, weight of the submitted tissue, or the Gleason score found in the initial random specimen. If only partial additional sampling was performed in our TURP specimens, upon finding less than 5% of tissue involved by cancer in the initial sample, cost savings in our institution would have been $78.72/case and a total of $2655.21/year. Calculated cost analysis was based on the technical and the pathologists' fees in our laboratory and reflected our practice scenario where grossing is done only by pathology assistants. In institutions where grossing of TURP specimens is done by a pathologist, this additional cost should also be considered.

The small sample size of this study requires confirmation by studies performed in other institutions before changing the current CAP practice guidelines.

Written by Kiril Trpkov, MD, FRCPC, as part of Beyond the Abstract on UroToday.com.

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