Use of Intervening Unstained Slides for Immunohistochemical Stains for High Molecular Weight Cytokeratin on Prostate Needle Biopsies

Abstract

Immunohistochemical stains (IHC) stains for high molecular weight cytokeratin (HMWCK) may show the presence or absence of basal cells in a small focus of atypical glands helping to establish a benign or malignant diagnosis respectively. From January 1994 to the present, we have generated intervening unstained slides on all prostate needle biopsies for potential IHC stains for HMWCK because lesions may not survive deeper sectioning into the block. Of 1105 prostate needle biopsy cases seen at Johns Hopkins from January 1994 to December 1996, IHC staining for HMWCK was initially done on 94 (8.5%). To see whether lesions would still have been present for evaluation if we did not have intervening slides, we repeated the IHC stains for HMWCK off the paraffin blocks in 74 cases for which material was available for study. Care was taken not to trim the blocks. In 52 cases, the original HMWCK helped to establish a diagnosis; in 31 of these cases the lesion was not present on repeat IHC stains from the block. Of these 31 cases, the original HMWCK from intervening unstained slides helped to establish cancer (n = 23) or a benign (n = 8) diagnosis. The use of intervening unstained slides was critical to establish a diagnosis in 31 (2.8%) of 1105 prostate needle biopsies and saved the cost of repeat biopsy ($68,200) and spared these patients from a second surgical procedure.

Current practice of diagnosis and reporting of prostate cancer on needle biopsy among genitourinary pathologists

“…It has been suggested that unstained sections on intervening levels be retained to decrease the risk that a small focus suspicious for cancer is lost at recut for immunohistochemistry [13]. Such sections were critical to establish a diagnosis in 2.8% of cases in one study [13].…”

“…Such sections were critical to establish a diagnosis in 2.8% of cases in one study [13]. Whether it is possible to use this method routinely depends on the economic resources of the laboratory.…”

High-grade prostatic intraepithelial neoplasia

“…92 We routinely generate unstained intervening sections of all prostate biopsies for possible immunohistochemical staining, recognizing that small foci of concern are often lost when the tissue block is recut; one study reported loss of the suspicious focus in 31 of 52 cases. 93 Other markers of basal cells include proliferation markers, differentiation markers, and genetic markers. The preferential localization of many of these markers in basal cells but not in secretory cells suggests that they play a role in growth regulation.…”

A new core‐biopsy instrument with an end‐cut technique provides prostate biopsies with increased tissue yield

“…In some laboratories, this is compensated for by routinely taking an intervening section between the levels. According to Green et al [19], the intervening section was necessary to establish a diagnosis in 2.8% of cases, but this is a time-consuming and relatively expensive routine in a busy practice. By using the endcut needle, the length of the specimen that is not seen in the histological section is decreased from 18.5% to 13.5%.…”