الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Background: Breast cancer is reported as one of the most common cancers among females worldwide. Infectious agents especially viruses have been considered as role players in the development of breast cancer. Several recent studies have suggested a possible relationship between BLV infection and breast cancer in human. Due to the high incidence and mortality rates of breast cancer, it is important to find new risk factors that might be associated with the stimulation and development of breast cancer. Although some investigations suggest an association between BLV and breast cancer, the involvement of this virus as a risk factor remains controversial. Aim: This work was carried out to determine the presence of tax gene segment of BLV in paraffin-embedded breast tissue samples and to determine the risk factors for BLV infection in humans. Setting: Oncology Center pathology Laboratory, Mansoura University and Microbiology Diagnostics and Infection Control Unit (MDICU), in the Medical Microbiology and Immunology Department, Faculty of Medicine, Mansoura University. Results: This study was conducted over a period of 24 months starting from June, 2020 till end of May, 2022, and included 100 FFPE breast tissue specimens. group (I) enrolled fifty FFPE breast cancer tissue specimens from patients between 29-76 years, and group (II) enrolled fifty FFPE breast tissue with benign lesions from patients between 23-76 years. Bovine leukemia virus Tax gene was detected by nested PCR in 8 (16%), and 2 (4%) samples of group I and group II, respectively. There was statistically significant difference between group I and II (P value =0.04). BLV infection can increase the risk of breast cancer development five times (OR = 4.6). Non-significant difference was detected between BLV DNA and histopathological type in group I. Six positive BLV samples from group I were IDC, 75 %, and only 2 (25 %) were ILC. There was no statistically significant association between the presence of BLV DNA and grading, staging or LN metastasis. There was no statistical significance observed between the proliferative rate and the presence of BLV DNA (P=0.282). The results obtained in this study showed that there was no association observed between tumor prognostic biological markers such as (ER, PR , HER-2 oncoprotein) and the presence of BLV DNA in tissues (P value = 0.148, 0.736, 0.686 respectively). Regarding the risk factors for BLV infection, statistically significant differences correlate the BLV infection and people from rural area than urban and those with home-based activities than others occupational activities. Conclusion: This study support the presence of BLV in human breast tissue raising the hypothesis that BLV infection could be a risk factor for the development of breast cancer in human. People from rural areas and those with home-based activities are at risk for BLV infection than others.