Is breast cancer in women caused by bovine leukaemia virus and Mycoplasma spp.? An investigation from South Brazil

Bovine leukaemia virus (BLV) is a widespread Deltaretrovirus that remains mostly asymptomatic in cattle but can lead to B-cell lymphoma. Evidence suggests that BLV may infect humans and has been associated with breast cancer. Mycoplasma spp. are bacteria linked to various human diseases, including cancer. This study investigated the presence of BLV and Mycoplasma spp. DNA in fresh and formalin-fixed paraffin-embedded (FFPE) breast tissue and leukocyte samples from 100 women undergoing breast surgery in South Brazil. Polymerase chain reaction (PCR) and nested-PCR targeted four BLV genes in fresh tissue and leukocytes, and two genes in 30 FFPE samples from 21 patients. Fresh tissue was also tested for Mycoplasma spp. One fresh breast tissue sample was positive for the BLV tax gene, confirmed by Sanger sequencing. All leukocyte and FFPE samples were negative for BLV. Mycoplasma spp. DNA was not detected in any fresh tissue sample. Compared to previous studies reporting BLV DNA in fresh tissue from Colombian women and FFPE samples in Brazil, our findings show a lower frequency. The negative results in leukocytes and FFPE samples support the hypothesis that most women in this study were not infected with BLV or Mycoplasma .