Background: Bovine Leukemia Virus (BLV) is known by infections in bovine cattle and produce, in 30% of infected animals, persistent lymphocytosis significantly impacts the beef industry. It has been proposed that this virus could be transmitted to humans and be present in cases of breast cancer. Aim: to determine the presence of 380 bp of gag gene segment of BLV in paraffin-embedded breast tissue. Study Design: Control-case study. Methodology: 106 tissue samples were collected. 53 were cancer positive samples and 53 were negative samples for this pathology. After dewaxing tissues, DNA was extracted, amplified and sequenced. Phylogenetic analysis was done in order to verify BLV gene segment, presence and origin. Results: 43 samples were positive (40.5%) for BLV segment. In the case group this segment was found in 35.8% of the samples and in the control group, BLV presented in 45.2% of the samples. Phylogenetic analysis confirmed BLV presence and had shown a high homology between amplified gene sequences obtained from human breast tissues and those coming from bovine cattle with leukosis reported by GenBank. Conclusion: The presence of BLV genes in humans and its location in breast tissue can be confirmed, however, it should be clarified as a possible promoter of malignancy processes on this tissue.