Alpha-methylacyl-CoA racemase (AMACR) has recently been shown to be a highly sensitive marker for the diagnosis of
prostate cancer. However, there is limited information concerning its utility as a marker for prostate
carcinoma after hormonal
therapy. Our current investigation was conducted to evaluate the expression of AMACR in patients with prostate
carcinoma after hormonal
therapy and assess its diagnostic utility in combination with p63 and high molecular weight
cytokeratin (34betaE12) staining. Prostate tissues from 49 patients who had been treated with hormonal
therapy were immunohistochemically analyzed for AMACR, 34betaE12, and p63 expression by a triple
antibody cocktail stain. The staining intensities and the percentages of positively staining
tumor cells were recorded. The correlations between AMACR expression and metastatic status, associated hormonal
therapy regimens, and the extent of
hormone therapy effect were analyzed. All malignant acini were completely negative for both basal cell markers (34betaE12 and p63).
Tumor cells failed to demonstrate expression of AMACR in 14 (29%) of 49 cases. In the remaining 35 cases (71%), positive immunostaining for AMACR was noted, but with variable intensities and percentages of cells stained. Positive staining for AMACR in benign glands was not seen in any case. In all cases, basal cells were strongly stained by p63 in benign acini with a mean positive percentage of 96%. Similarly, basal cells in benign acini displayed moderate staining intensities for 34betaE12 in 3 (7%) of 41 cases and strong immunostaining for this marker in the remaining 38 cases (93%); the mean percentage of positive cells was 92%.
alpha-methylacyl-CoA racemase expression may be substantially diminished or entirely lost in prostate
carcinoma after hormonal
therapy. This variation in AMACR expression does not correlate with the metastatic status, the modality of hormonal
therapy, or the extent of
therapy-related effect. It is important that pathologists be aware that some hormonally treated prostate
carcinomas do not express AMACR, and that immunostaining in such cases must be interpreted with caution. A triple cocktail
stain using AMACR, 34betaE12, and p63 can be helpful in evaluating prostate specimens for the presence of residual or recurrent
carcinoma after hormonal
therapy for
cancer.