Objective: Claudin family of proteins has been shown to be overexpressed in various cancers. We aimed to investigate one member of this family, the Claudin-3 expressions in prostate tissue and evaluate its utility as a diagnostic marker for prostatic adenocarcinoma.

Material and Method: A total number of 50 cases of prostatic adenocarcinoma were reviewed from the files of M.H Ankara Dışkapı Research and Training Hospital. One paraffin block was selected for each case. For separate immunohistochemical staining with Alpha-methylacyl-CoA racemase (AMACR) and Claudin-3, two slides were sectioned from each block. Prostatic carcinoma (PC), Benign gland, and High grade prostatic intraepithealial neoplasia (HGPIN) components in each slide were evaluated. Afterwards the intensity of stainings were scored on a scale of 0-2 seperately for each component.

Results: After immunohistochemical evaluation, 94.1% of PC showed positivity with Claudin-3 whereas this value was 77.4% for AMACR. Furt-hermore in the areas of HGPIN, the positivity rates with Claudin-3 was also higher than those of AMACR (p <0.005).

Conclusion: In statistical analysis, Claudin-3 appeared to be a reliable immunohistochemical marker for PC at least as much as AMACR. We think that our findings strongly suggest the use of Claudin-3 as an alternative for AMACR in the routine tissue diagnosis of PC.