Differential immunohistochemical expression of AMACR and ERG in prostatic lesions

Abstract

Introduction Alpha-methylacyl-CoA (AMACR) is an enzyme of the mitochondria and perixosomes. It was found that it showed great overexpression in prostatic adenocarcinoma, even with minimal foci. TMPRSS2/ERG fusion is one of the common genetic anomalies affecting PCa. A great correlation between positive immunohistochemical (IHC) expression for ERG and the state of fusion has been found, but the diagnostic and prognostic importance of ERG IHC remains undetected. This study aimed to evaluate the differential diagnostic and prognostic significance of both AMACR and ERG in PCa with correlation to the clinicopathological variables.Materials and methods TThe authors reviewed 70 prostatic lesions. Prostatic adenocarcinoma (50 cases), prostatic intraepithelial neoplasia (PIN) (15 with high-grade PIN, five with low-grade PIN), and benign prostatic hyperplasia (10 cases) that were used as a control. Immunohistochemical staining for AMACR and ERG was done. Follow-up of the cases for 18 months was also done.Results A statistically significant difference in the expression of ERG among the examined cases was found. It was negative in control benign prostatic hyperplasia and low-grade PIN cases), positive in 20% of high-grade PIN, and 74% of prostatic adenocarcinoma cases (P<0.01). No statistically significant correlation was found between ERG expression and tumor volume, Gleason sum score, stage, surgical margin, presence of lymphovascular invasion, perinural invasion, distant metastasis, and survival (P>0.05). Regarding AMACR expression, a statistically significant difference in the expression of AMACR among the examined cases was found (negative in benign prostatic hyperplasia, and low PIN cases) to be positive in 33.3% of high-grade PIN and in 62% of prostatic adenocarcinoma cases (P<0.01). A statistically significant correlation was found between AMACR expression and tumor volume, Gleason sum score, surgical margin, presence of lymphovascular invasion, and survival (P<0.05).Conclusion The study provides an additional evidence that IHC expression of AMACR has a role in prostatic carcinoma development. IHC expression of AMACR was absent in benign prostatic lesions. AMACR is an essential tumor marker for the diagnosis and prognosis of prostatic lesions. IHC expression of ERG may have a role in the diagnosis and biological stratification of prostate cancer.