Rectal Tissue In Prostate Biopsy Specimens Can Mimic Prostate Cancer

UroToday.com - Prostate biopsies, similar to other organ biopsies involve placing the biopsy needle through other organs or structures in order to obtain the desired study tissue. Rectal tissue is commonly included with prostate biopsy specimens, and as another glandular tissue, rectal tissue can be misdiagnosed as prostate cancer (CaP).

Drs. Schowinsky and Epstein from the Johns Hopkins University School of Medicine report histologic findings that occur in rectal tissue on prostate biopsy specimens that mimic CaP. Their report appears in the July 2006 issue of the American Journal of Surgical Pathology.

A group of 16 biopsy specimens from 14 patients referred to the authors between 1996 and 2005 were evaluated. In 15 of 16 biopsies (94%), rectal glands were present only as a single focus. In 63%, the rectal glands were present on detached fragments of tissue and in 1 case the glands were involving adipose tissue at the end of a biopsy core. Blue mucin was detected in 63% of rectal glands, and is seen in approximately 33% of prostate biopsies with minimal cancer. Goblet cells were noted in 44% of cases and elements of loose connective tissue consistent with lamina propria were found in 75% of cases.

At a cellular level, mitotic activity was noted in 37% and prominent nucleoli were seen in 37%. Inflammation was found in 63% of cases. A triple immunoperoxidase stain for p63, high molecular weight cytokeratin (HMWCK) and _-methylacyl-coA racemase (AMACR) was used in 4 cases as rectal glands lack basal cells and thus stains for HMWCK and p63 should be negative. In 3 cases, p63 and HMWCK were negative and AMACR was positive. This is likely due to the fact that AMACR is positive in over 70% of rectal tissue. In the 4th case all three stains were negative.

The excellent photographs in this manuscript illustrate the descriptions of the histologic features. In general, rectal glands on prostate biopsy tend to be in detached fragments or at the end of a core sample, in a single focus and associated with loose connective tissue consistent with lamina propria.

By Christopher P. Evans, M.D.

Am J Surg Pathol 2006;30:866-70
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