Alpha methylacyl‐CoA racemase (AMACR) in prostate adenocarcinomas from Japanese patients: Is AMACR a “race”‐dependent marker?

BACKGROUND: Alpha methylacyl-CoA racemase (AMACR) is a useful diagnostic marker for prostate adenocarcinoma. However, its usefulness has not been fully validated in Japanese patients. The aim of this study was to evaluate the diagnostic utility of AMACR in prostate needle biopsy examination in Japanese patients. METHODS: A total of 119 prospective consecutive prostate needle biopsy specimens (680 cores) obtained from Japanese patients were examined. Sixty patients had adenocarcinoma (adenocarcinoma, 160 cores; benign, 204 cores), 14 patients had high-grade prostatic intraepithelial neoplasia (HGPIN; 19 cores), and 45 patients did not have any neoplastic lesions (297 cores). AMACR expression was scored semi-quantitatively as 0 (no expression), 1+ (partial and/or weak expression), or 2+ (strong, circumferential expression). The number of positively stained glands was counted. RESULTS: 2+ AMACR expression was observed in 70.1% of adenocarcinoma cases and in 52.6% of HGPIN cases. Of the adenocarcinoma cases showing 2+ AMACR expression, 34.8% demonstrated a heterogeneous expression pattern, with 1-75% of AMACR-positive glands. Three hundred eighty-five of the benign glands with an adenocarcinoma component showed 2+ AMACR expression (35 cases, 94 cores). 2+ AMACR expression was observed in 67 non-neoplastic benign glands (9 cases, 19 cores). CONCLUSIONS: The sensitivity and specificity of AMACR for the diagnosis of prostate adenocarcinoma and benign glands in Japanese patients are lower than those previously reported in Western countries. Pathologists should be cautious while interpreting AMACR expression pattern in Japanese patients.