Limited evidence of human papillomavirus on breast tissue using molecular in situ methods

Background: Human papillomavirus (HPV) has been proposed as an etiologic agent of breast cancer based on numerous reports of high-risk (oncogenic) HPV types in malignant breast tissues. However, most of those studies used standard and nested solution polymerase chain reaction (PCR) techniques, both of which are disadvantaged by vulnerability to laboratory contamination from positive control DNA and the inability to localize the signal to a specific cell type. To overcome these drawbacks, the authors of this report explored the use of in situ molecular methods of viral detection to reassess the frequency of HPV in malignant breast tissue. Methods: In situ hybridization (ISH) was used with probes that were specific for the capsid region of 12 oncogenic HPV types, and in situ PCR (IS-PCR) was used with primers that were specific for the capsid region of HPV-16, which is the most common oncogenic HPV type. These methods were resistant to molecular contamination and allowed identification of the positive cell type. The specimens examined were malignant tissues from patients with 70 breast cancer patients at The University of Texas M. D. Anderson Cancer Center in Houston, Texas. Results: HPV was observed in 4 of 70 specimens (5.7%) using ISH and in 2 of 70 specimens (2.9%) of specimens using IS-PCR. Concordance between the 2 methods was high for negative specimens; both methods yielded negative results in 66 of 70 specimens (94.3%). However, there was no concordance for the few positive specimens, probably because of differences in sensitivity and the targeted HPV types. Conclusions: Oncogenic (high-risk) HPV types were present in malignant breast epithelium very infrequently and, thus, may be causative agents of only a relatively small proportion of all breast cancers.