Immunohistochemical Expression of Prostate Stem Cell Antigen )PSCA) in Prostatic Carcinoma

Abstract

Prostate cancer is one of the most common leading causes of cancer related death in men worldwide. There is always a requirement for new diagnostic and prognostic markers that discriminate between indolent and aggressive variants. The present study was conducted on 20 cases of benign prostatic hyperplasia (BPH), 20 cases of prostatic intraepithelial neoplasia (PIN) as well as 40 cases of prostatic carcinomas (PCa) collected from Pathology Department and Pathology Lab of Ain-Shams University Hospitals during the period from January 2006 to December 2010. The aim of this study was to evaluate immunohistochemical prostate stem cell antigen (PSCA) protein expression in these lesions and to investigate its association with the different clinicopathological parameters of prostatic carcinoma. Clinical data of all cases were reviewed as regard age, preoperative serum prostate specific antigen (PSA) level and weight of the prostate. Histopathologic study was done by reviewing the H&E slides for confirmation of the diagnosis, examination of the PIN cases for grade, pattern of high grade PIN and associated pathology (BPH or prostatic adenocarcinoma). Examination of the malignant group was done for histologic typing, tumour quantitation, Gleason patterns as well as Gleason scores, pathologic TNM staging of radical prostatectomy specimens, presence of lymphovascular invasion, perineural invasion and presence or absence of bilharzial ova. Immunohistochemical examination for PSCA protein and correlation of its expression with the different clinico-pathological features were done. This work revealed that 20% of BPH cases showed negative expression and 60% showed weak expression with no recorded strong expression levels. In low grade PIN (LGPIN), the majority of cases (66.6%) showed weak PSCA expression. However, no cases showed strong PSCA expression. In HGPIN, 57.1% of cases showed moderate PSCA expression and 28.6% of cases showed strong PSCA expression while only 14.3% of cases showed weak expression., HGPIN cases showed significantly higher levels of PSCA immunohistochemical expression than LGPIN and BPH cases (p= 0.005). PSCA expression in adenocarcinoma was moderate in 45% of cases and strong in 45% of cases. A significantly higher levels of PSCA protein expression than PIN and BPH (p=0.0001) was revealed. However, no statistical significant difference was found between HGPIN and prostatic adenocarcinoma (p= 0.555). Regarding HGPIN patterns in the present study, tufting and mixed patterns were the commonest patterns (35.7% each). The micropapillary pattern showed the highest levels of immunohistochemical expression of PSCA (p=0.03). This study revealed no significant relationship between PSCA expression levels versus age, serum PSA level and weight of the prostate (p>0.05). The current study also revealed a positive relationship between PSCA expression levels and tumour percentage being stronger in tumours occupying more than 50% of prostatic tissues (p = 0.0001) while no relationship between PSCA expression and the presence of perineural invasion in prostatic adenocarcinoma (p=0.6193). A statistical significant relationship between high PSCA expression levels and high grade tumours (P = 0.001) was revealed. Tumours with extraprostatic extension (pT3) showed statistically higher PSCA expression than tumours confined to the organ (pT2) with (p= 0.02). On the contrary, PSCA expression levels showed no relationship with lymph node invasion (pN0 versus pN1) with a p value of 0.08.