Immunohistochemistry Is Rarely Used in the Evaluation of Prostate Needle Biopsy Material with Lesions > 3 mm in Linear Extent
Omar Hameed, Leonard I Bloom, Chura Salih, Peter A Humphrey. Vanderbilt University, Nashville, TN; Washington University, St. Louis, MO
Background: Immunohistochemistry (IHC) is increasingly being used in the evaluation of prostate needle biopsy material with emerging data indicating some degree of over utilization and potential misuse of IHC in particular settings. Accordingly, identification of histological findings more or less likely associated with its use could potentially provide evidence-based guidelines for optimal and more cost-effective utilization. The aim of this study was to specifically evaluate different measures of extent in this context.
Design: Consecutive prostate biopsies in which the diagnosis of carcinoma was contemplated and further evaluated by IHC were reviewed to determine the number of involved cores with atypical/carcinomatous foci, the linear extent of such lesions and whether or not they represented ≤5% of core tissue. These data were compared to those obtained from prostate biopsies collected in the same one year period in which the diagnosis of carcinoma was made without utilizing IHC.
Results: Of 318 reviewed cases, there were 255 diagnosed (as carcinoma) without IHC and 63 cases for which IHC was needed for the diagnosis. These latter cases represented 10.3% of all biopsies evaluated within the study period and included 38 (60%), 18 (29%), 4 (6%) and 3 (5%) eventually diagnosed as carcinoma, focal glandular atypia, high-grade prostatic intraepithelial neoplasia and benign, respectively. Compared to the remainder, cases utilizing IHC were significantly (P < .0001) more likely to have lesions limited to one core (79% vs 30%), involving ≤5% of core tissue (90% vs 31%) or ≤3mm in linear extent (97% vs 31%). The proportion of cases needing IHC progressively decreased with increasing linear extent (Figure). This was also evident when the entire cohort was considered together as shown in the table.
|Linear Extent (mm)||% IHC (95% CI)|