Immunohistochemical Expression of Alpha-Methyl-Coa (AMACR) and ERG in Prostatic Adenocarcinoma and Prostatic Hyperplasia: A Comparative Study

OBJECTIVE: This observational comparative study aimed at investigating the diagnostic accuracy of ERG in differentiating benign and malignant prostatic lesions and comparing it to the diagnostic accuracy of AMACR. We also aimed at comparing AMACR and ERG expression to Gleason grade of the carcinoma cases. METHODS: Seventy- two cases (22 prostatic hyperplasia and 50 prostatic carcinoma) were collected from the pathology department at Cairo university. The cases were immunostained by antibodies against AMACR and ERG. Immunohistochemical expressions of both markers were differentially examined in benign and malignant cases, compared to each other’s, as well as, to the grade group of the malignant cases. RESULTS: AMACR showed 62% sensitivity and 86.4% specificity for the diagnosis of PC, with a statistically significant differential expression in benign and malignant lesions (P=0.001). Its expression also correlated significantly with the age (p=0.007), Gleason grade (P=0.006) and perineural invasion (P=0.011). Although ERG showed 100% specificity to PC with no expression in hyperplasia cases, it showed only 22% sensitivity for PC cases. ERG expression also showed statistically significant correlation with the Gleason grade. No association between ERG and AMACR expression was detected in our study (P=0.151). Regarding the diagnostic accuracy, although ERG accuracy was much lower than that of AMACR, combining both markers yielded a higher diagnostic accuracy. CONCLUSION: Although ERG proved no superior value than AMACR in diagnosing prostatic lesions, combining both markers may lead to higher diagnostic accuracy owing to higher ERG specificity for PC.