Introduction & Objective: Prostatic carcinoma is the most common malignancy throughout the world among the males over middle age and the second leading cause of cancer-related deaths in western countries. The currently most established prognostic factors in prostatic carcinoma are histological grade (Gleason system) and tumor stage .Various new prognostic factors that have been suggested to provide additional information include proliferative activ-ity (Ki-67 labeling index),over expression of the oncogene bcl2 and Her2-neu and inactiva-tion of the p53 tumor suppressor gene. The aim of this study was to compare p53, Ki-67, bcl2 and Her2-neu biomarkers frequency in low grade and high grade prostatic carcinoma.

Materials & Methods: In this cross sectional study, 76 cases of prostatic carcinoma patients with different combined Gleason score were studied after they had been admitted to the pathology wards of Beheshti and Be’sat hospital in Hamadan city between 2006-2011.Age, Combined Gleason's score and histologic grade record in each case. p53, Ki-67, bcl2 and Her2-neu ex-pression were investigated immunohistochemically .The biomarkers of p53, Ki-67, bcl2 and Her2-neu between low grade and high grade prostatic carcinoma were compared. The tumors were considered low grad when Gleason score was 6 or less, and high grad when the Gleason score was 7 to 10.

 Results: This investigation revealed that the frequency of p53, bcl2, Her2-neu and Ki-67 ex-pression is 68.4%, 34.2%, 78.9% and 52.6%, respectively. In this study 81.6% of high grade and 55.3% of low grade tumors were immunoreactive for p53 (P=0.013). Over expression of bcl2 was found in 36.8% of high grade and 31.6% of low grade of prostatic carcinoma (P=0.405). 81.6% of high grade and 76.3% of low grade carcinoma were positive for Her2 –neu (P=0.390). Ki-67 positivity was found in 68.4% of high grade and 36.8% low grade car-cinoma (P=0.006).

 Conclusion: The most important findings of our study are that the frequency of p53 and Ki-67 proteins expression is correlated with high grade of prostatic carcinoma. However, there was not any significant difference of bcl2 and Her2-neu biomarker in the two grades of prostatic carcinoma.