Alpha-methylacyl-CoA-racemase expression in variants and unusual patterns of prostate carcinoma

Introduction: Alpha-methylacyl-CoA-racemase (AMACR) is a tumor marker expressed in prostate cancer. Literature data concerning its expression in different variants and unusual patterns of prostate carcinoma are uneven and less numerous. The present study investigates the AMACR expression in some rare forms of prostate carcinoma. Material and methods: Distinct variants and unusual patterns of prostate carcinoma (in pure or mixed form) were selected: foamy gland (9 cases), ductal adenocarcinoma (7 cases), pseudohyperplastic (5 cases), atrophic (3 cases), urothelial (3 cases), mucinous (2 cases), signet ring cell carcinoma (1 case) together with 20 cases of conventional prostate carcinomas. IHC study was performed using the following antibodies: AMACR, high molecular weight cytokeratin HMWCK, p63, PSA, prostein, CK5/6, CK7 and CK20. Results: Ninety percent of conventional prostate carcinomas cases were positive for AMACR. 5 out of the 30 variants/unusual patterns of prostate carcinoma cases were devoid of immunoreactivity for AMACR, including 2 ductal adenocarcinomas, 2 urothelial and an atrophic carcinoma. Carcinomas/areas of foamy, pseudohyperplastic and mucinous type have shown a marked heterogeneous expression of AMACR, with negative areas and foci of variable intense positive staining. Conclusions: This study confirms the heterogeneity of AMACR expression in prostate carcinomas and the fact that this marker's expression is reduced/absent in some cases of conventional or variants/unusual patterns of prostate carcinomas. In difficult cases or small biopsy specimens, the diagnosis of cancer should be based on correlation of data offered by the usual stains with findings provided by immunostaining for basal cells and AMACR.