CONTEXT: Immunohistochemical (IHC) stains have known utility in prostate biopsies and are widely used to augment routine staining in difficult cases. Patterns in IHC utilization and differences based on pathologist training and experience is understudied in the peer-reviewed literature. OBJECTIVES: To compare the rates of IHC usage between specialized (genitourinary; [GU]) and nonspecialized (non-GU) pathologists in extended core prostate biopsies (ECPBs) and the effects of diagnosis; and in cancer cases Gleason grade, disease extent, and perineural invasion on the rate. DESIGN: Consecutive ECPBs from 2009-2011 were identified and billing data were used to determine the number of biopsies and IHC stains per case. Diagnoses were mapped and in cancer cases, Gleason grade, extent of disease, and perineural invasion were recorded. Pathologists were classified as GU or non-GU on the basis of training and experience. RESULTS: A total of 618 ECPBs were included in the study. Genitourinary pathologists ordered significantly fewer IHC tests per case and per biopsy than non-GU pathologists. The rate of ordering was most disparate for biopsies of cancerous and benign lesions. For biopsies of cancerous lesions, high-grade cancer, bilateral disease, and perineural invasion decreased the rate of ordering in both groups. In cancer cases, GU pathologists ordered significantly fewer stain tests for highest Gleason grade of 3 + 3 = 6, for patients with focal disease and for patients with multiple positive bilateral cores. The effect of the various predictors on IHC ordering rates was similar in both groups. CONCLUSIONS: Genitourinary pathologists ordered significantly fewer IHC stain tests than non-GU pathologists in ECPBs. Guidelines to define when IHC workup is necessary and not necessary may be helpful to guide workups.

Background: Ancillary immunohistochemical (IPOX) stains are useful in clarifying diagnostically challenging pathologic specimens. In diagnostic workup of prostate needle biopsies, stains for basal cells and α-methylacyl coenzyme A racemase are routinely used to support or refute the diagnosis of prostate cancer. Although useful, these stains add cost and must be used judiciously. There is a lack of firm guidelines establishing the proper utilization of IPOX studies in prostate pathology. Therefore, differences in patterns of stain use and diagnoses may exist, related to expertise of the pathologist. Objectives: The purpose of this study was to compare patterns of diagnoses and IPOX stain use in extended core prostate biopsies between genitourinary (GU) and non-genitourinary (NGU) pathologists in the University of Massachusetts Medical Center Pathology department. Methods: By computer search of medical records, consecutive extended core prostate biopsies (6+ cores) from years 2006-2011 were identified. Using Current Procedural Terminology (CPT) billing data, the number of cores and number of IPOX stains were retrieved. Diagnoses were recorded. Pathologists were divided into two groups based on expertise: genitourinary and non-genitourinary. Differences in the patterns of IPOX use and diagnoses between the two groups were analyzed. Results: GU pathologists diagnose significantly higher rates of prostate cancer (43.8% vs. 35.8%, p Conclusion: Significant differences exist in patterns of IPOX usage between GU and NGU pathologists in extended core prostate biopsy in this single institution study. This suggests the need for guidelines and continuing education focused on this issue to standardize practice, an intervention likely to improve quality of diagnoses and to reduce unnecessary costs.