In Iraq, breast cancer incidence exceeds any other type of cancers and the etiology not understood well.Epstein Barr virus is a gamma herpesviruses and one of carcinogenic viruses that may implicated tobreast carcinogenesis. The nuclear antigen-1 (EBNA-1) protein is the sole EBV antigen that presentedin all tumors related to EBV and plays pivotal roles in carcinogenesis of the virus. Examination appliedby immunohistochemistry (IHC) to detect and demonstrate the correlation between (EBNA-1) and tumorsuppressor protein (P53) expression. The study includes paraffin-embedded tissue blocks of ninety 90malignant breast tissues and thirty 30 normal breast autopsies. EBNA-1 was significantly expressed in 40/90(44.4%) of malignant tissues while its expression in normal breast tissues was negative in all tested cases.The tumor suppressor protein P53 was showed negative expression in all normal breast tissues and positivein 27/90 (30%) in malignant breast tissues. A significant negative relationship (r=-0.420; P<0.05) revealedbetween EBNA-1and P53 expression. These finding reveal that EBNA-1 was evident in malignant breasttissues and demonstrate the interplay between EBV and p53 raising the possibility that viral infection maybe involved in carcinogenesis process
