Correlations of PTEN and ERG Immunoexpression in Prostate Carcinoma and Lesions Related to Its Natural History: Clinical Perspectives

Purpose: The aim of our study was to observe the associations between the ETS-related gene (ERG) and the phosphatase and tensin homolog gene (PTEN) immunoexpression in prostate cancer and related lesions and highlight the clinical significance of these findings. Methods: We evaluated the immunohistochemical expression of ERG and PTEN in a series of 151 invasive prostate adenocarcinomas, including low-grade (Gleason grade pattern 3) and high-grade (Gleason grade patterns 4, 5) morphological patterns which corresponded to 45.5% and 54.4% of the cases, respectively. Additionally, we evaluated the immunoexpression of the two markers both in foci of high-grade prostatic intraepithelial neoplasia (HGPIN), as a precursor lesion of cancer, and in foci of intraductal carcinoma of the prostate (IDCP). Finally, to ensure the malignant nature of the prostate glands examined, we employed p63 and alpha-methylacyl-CoA racemase (AMACR) expression. Results: We found that PTEN loss was observed in 50.7%, and ERG positivity was detected in 41.8% of our cancerous samples. In HGPIN, PTEN loss appeared to be linked with a high-grade adjacent invasive carcinoma component which also displayed PTEN loss. As far as IDCP is concerned, ERG immunonegativity was correlated with adjacent high-grade invasive cancer, which was also ERG immunonegative. Conclusions: Our findings suggest that the clonal expansion of invasive cancer appears to be associated with distinct immunophenotypic cellular alterations of both early and late cancer-related histological lesions. Patients with PTEN loss in HGPIN in prostate biopsies should be closely monitored due to the increased likelihood of having an associated invasive high-grade carcinoma that may have not been sampled. Given the clinical significance that derives from PTEN expression in HGPIN lesions, we suggest the routine use of PTEN immunohistochemistry in prostate cancer biopsies in which HGPIN is the only finding.