(α-methylacyl-CoA racemase)
AMACR (P504S protein, 48 kDa) plays a role in the beta-oxidation of branched-chain fatty acids and their derivatives. AMACR is found in mitochondria and peroxisomes of numerous tissues such as prostate, liver, biliary tract, kidney and lung. Using immunohistochemistry, non-neoplastic prostate show a weak or focal staining reaction in about 20% of the cases. The reactivity tends to decrease with age but the correlation coefficient is low.
A diffuse staining pattern for AMACR has been found in more than 90% of prostate carcinomas irrespective of Gleason score. Particularly foamy, pseudohyperplastic and atrophic variants of carcinoma may be negative. In prostatic intraepithelial neoplasia (PIN), the positive rate of AMACR ranges from 13% to 72%.
AMACR is mainly used in prostate lesions. Since negative staining for high molecular weight cytokeratin (HMW-CK) in atypical prostate glands may not be sufficient for a definitive diagnosis of malignancy, p63 may enhance the ability to diagnose limited prostate cancer. However, AMACR should always be used in conjunction with (HMW-CK) and/or p63. A cocktail staining is applicable. It is also important to note that AMACR positive glands in a prostate biopsy may represent seminal vesicle or periurethral glands.
Normal prostate is recommendable as negative control and normal kidney as positive control.
Selected references
Gologan A, Bastacky S, McHale T, Yu J, Cai C, Monzon-Bordonaba F, Dhir R. Age-Associated Changes in Alpha-Methyl CoA Racemase (AMACR) Expression in Nonneoplastic Prostatic Tissues. Am J Surg Pathol. 2005 Nov;29(11):1435-41. Hameed O, Humphrey PA. p63/AMACR antibody cocktail restaining of prostate needle biopsy tissues after transfer to charged slides: a viable approach in the diagnosis of small atypical foci that are lost on block sectioning. Am J Clin Pathol. 2005 Nov;124(5):708-15. Jiang Z, Woda BA. Diagnostic utility of alpha-methylacyl CoA racemase (P504S) on prostate needle biopsy. Adv Anat Pathol. 2004 Nov;11(6):316-21. Kunju LP, Chinnaiyan AM, Shah RB. Comparison of monoclonal antibody (P504S) and polyclonal antibody to alpha methylacyl-CoA racemase (AMACR) in the work-up of prostate cancer. Histopathology. 2005 Dec;47(6):587-96. Varma M, Jasani B. Diagnostic utility of immunohistochemistry in morphologically difficult prostate cancer: review of current literature. Histopathology. 2005 Jul;47(1):1-16.
21.05.15 - MV/LE