Diagnostic utility of immunochemical technique using p63 and Alpha Methylacyl Coenzyme A Racemase (AMACR) in the diagnosis of core-needle biopsy of the prostate: Experience in a tertiary academic institution in Nigeria

Abstract

Background: Prostate adenocarcinoma is one of the most common malignancies and a leading cause of cancer-related mortality among males worldwide. There are challenges associated with confident/equivocal diagnosis of prostate carcinoma on small prostate samples from core-needle biopsies diagnosed histologically because of certain mimickers of prostatic carcinoma. Hence, there is a need to improve the diagnostic accuracy of the histological diagnosis of core-needle biopsies by utilizing immunohistochemical profiling to overcome these challenges. The aim of this study was to use p63 and alpha-methylacyl coenzyme A racemase (AMACR) immunostains to confirm hematoxylin and eosin (H and E) diagnosed adenocarcinomas and clarify equivocal diagnoses as well as correlate the H and E diagnoses with immunohistochemical diagnoses. Materials and Methods: This was a 3-year retrospective study of core-needle prostatic biopsies processed at the Anatomic and Molecular Pathology Department of Lagos University Teaching Hospital, Lagos, Nigeria. The formalin-fixed paraffin-embedded tissue blocks were retrieved, and new slides were prepared in cases where old slides were faded. The routinely processed slides were reviewed and classified into the following categories: benign, malignant (adenocarcinoma), and equivocal lesions (i.e., lesions considered suspicious for adenocarcinoma). The cases diagnosed as adenocarcinoma and equivocal lesions were then subjected to immunohistochemistry (IHC) using p63 and AMACR monoclonal antibodies to confirm the diagnoses of prostate adenocarcinoma and clarify the equivocal diagnoses. Based on the findings on IHC, the cases were reclassified as either adenocarcinoma, benign or indeterminate lesions (i.e., lesions that could not be classified as either benign or adenocarcinoma due to poor staining quality). Results: A total of 221 prostatic core biopsies met the inclusion criteria for this study. Out of these, histological diagnoses of prostatic adenocarcinoma were made in 113 cases (51.1%), 86 cases (38.9%) were benign, while equivocal cases accounted for 22 cases (10%). The result showed that out of 113 H and E diagnosed prostatic carcinoma that were subjected to p63 and AMACR stains, 101 (89.4%) of them were found to be truly adenocarcinoma, while 7 (6.2%) were benign and 5 cases (4.4%) were indeterminate lesions. The results of p63 and AMACR on the 22 histologically diagnosed equivocal prostatic lesions showed that 13 (59.1%) of the cases were adenocarcinoma, 7 cases (31.8%) were benign while 2 cases (9.1%) were indeterminate lesions. These p63 and AMACR immunostain results on routinely diagnosed prostatic carcinoma and equivocal diagnoses showed a statistically significant difference in the diagnostic potential of p63 and AMACR IHC when compared to the H and E as a diagnostic tool (P ≤ 0.001). Conclusion: We conclude that although histopathological examination of H and E sections remains the gold standard in the diagnosis of prostatic adenocarcinoma, the adjunctive use of p63 and AMACR immunostains is of great value in confirming small foci of adenocarcinoma, resolving morphologically equivocal cases and excluding benign mimickers as confounder in the diagnosis prostatic adenocarcinoma in small prostate samples obtained by core-needle biopsy.