The interaction between cell death and cell proliferation determines the growth dynamics of all tissues including those of the breast. Disruption of the balance between proliferation and apoptosis is considered to be an important factor in the development and progression of tumors. In addition, because the etiology and progression of breast carcinoma remain unclear, novel mechanisms of disease pathogenesis and outcome need to be considered. In this context, recent interest has been focused on the possible association between Epstein-Barr virus (EBV), an oncogenic ubiquitous herpes virus, infection and breast cancer pathogenesis and prognosis. Therefore, this study aimed to investigate Human Epidermal Growth Factor Receptor (HER)-2 (also known as neu and c-erbB-2) oncogene over-expression and compare it to the extent of apoptosis, in addition to the possible existence of EBV infection in a variety of breast lesions, and the relation between these parameters and patients' clinicopathological characteristics. Accordingly, paraffin-embedded tissue blocks from 45 female patients with breast tumors operated on between the years 2003 and 2005 were retrieved. In addition, histopathological data including type, size, histological grade, and metastasis to the axillary lymph nodes were also obtained. The cases were grouped into two categories
Group (A): included 30 cases with breast cancinoma (4 in situ and 26 invasive). Group (B): included 15 cases with benign breast diseases (9 fibroadenomas and 6 fibrocystic changes with epithelial hyperplasia) as a control group. The expression of HER-2/neu protein was examined immunohistochemically using the HercepTest kit. The assay was performed according to the manufacturer's guidelines, and the results were scored on a (0 to 3+) scale. The HER-2/neu positivity was defined by cytoplasmic membrane staining of 2+ or 3+ intensity. Among the 30 breast carcinomas, HER-2/neu score was 0 in 7 cases (23.3%), 1+ in 11 (36.7%), 2+ in 9 (30%), and 3+ in 3 (10%). Therefore, twelve cases (40%) of breast carcinomas were categorized as HER-2/neu positive. Among the benign lesions, two out of 15 cases (13.3%) demonstrated a weak positive (2+) HER-2/neu staining. No significant difference was found in the HER-2/neu over-expression between benign and malignant breast lesions (P = 0.094). However, the difference was statistically significant when HER-2/neu scores were compared between benign and malignant breast lesions (P = 0.037). Another aspect of the study was to through insight on the extent of apoptosis in these samples using terminal deoxynucleotidyl transferase- mediated d UTP nick end-labeling (TUNEL) assay. The apoptotic index (AI) was expressed as the percentage of TUNEL positive apoptotic cells per the whole tumor cell population. Interestingly, the current study demonstrated an increase in the mean AIs in parallel with the biological aggressiveness of the breast lesion, being the lowest (0.24%) in fibroadenomas and the highest in invasive carcinomas (1.8%). Also, the mean AIs were significantly higher in malignant (1.72%) than benign (0.38%) breast lesions (P < 0.01). Furthermore, this study examined breast lesions for evidence of EBV existence by means of immunohistochemical analysis using monoclonal antibodies against EBV-encoded nuclear antigen 2 (EBNA-2) and EBV-transactivating immediate-early BZLF1 (ZEBRA) proteins. The nuclear expression of EBNA-2 was observed in 12 (40%) of the 30 breast carcinomas, while all benign samples were negative for this protein. On the other hand, ZEBRA protein was negative in all benign and malignant tissue samples. According to histopathological data of patients with breast carcinoma, the current study demonstrated that both HER-2/neu positive expression and high apoptotic counts were significantly associated with tumor size (P = 0.017, P = 0.045, respectively). Moreover, HER-2/neu over-expression was significantly associated with metastasis to the axillary lymph nodes (P = 0.042). In contrast, both HER-2/neu expression and AI did not demonstrate a significant association with other clinicopathological parameters (age, invasiveness, and histological grade) (P > 0.05). Also, no significant association was observed between EBNA-2 expression and worse patients' clinicopathological characteristics. Interestingly, the comparison between these parameters revealed a strong positive correlation between HER-2/neu over-expression and high apoptotic counts (P < 0.01). Similarly, EBNA-2-positive cases exhibited a significant association with HER-2/neu over-expression (P = 0.002) and high apoptotic indices (P = 0.025). In conclusion, the results of the current study might refer to the significance of high HER-2/neu scores and apoptotic counts in breast carcinogenesis and prognosis. Therefore, long follow up studies based on larger group of patients are recommended to shed more insight on their prognostic value as molecular tumor markers in breast cancer. In addition, the findings of this study strongly argued against an important role of EBV in breast cancer pathogenesis, but its significant association with both HER-2/neu over-expression and higher apoptotic indices might indicate a promising prognostic value for this virus in breast carcinoma, which needs to be confirmed by further larger studies using more than one technique for EBV detection so that a definitive conclusion could be drawn in this regard.