Exploring HPV as an Etiologic Factor for Breast Cancer

Abstract

Abstract Introduction/Objective Breast ducts communicate with skin, which can expose one to infectious agents. Recent studies demonstrate differences between breast microbiome in normal tissues versus tumor, suggesting a potential role in carcinogenesis. Human Papilloma Virus (HPV) is the etiologic factor in numerous cancers, and studies suggest it may play a role in breast carcinoma. A recent case report identified an analogue to HPV-related multiphenotypic sinonasal carcinoma in the breast. This sinonasal tumor, closely associated with HPV type 33, consists of adenoid cystic-like morphology, basaloid and/or squamous cytology and multi-lineage differentiation (ductal and myoepithelial). Our aim was to determine if HPV is a driver of breast carcinomas with the outlined phenotype by testing with immunohistochemistry (IHC) for p16 and in-situ hybridization (ISH) for High Risk HPV (HR-HPV) E6/E7 mRNA. Methods/Case Report Breast cases from 2010- June 2022 were searched with the terms “adenoid cystic,” “myoepithelial differentiation,” or “basaloid.” Cases of adenoid cystic carcinoma with a diagnostic fusion were excluded. Those with basaloid and/or squamous morphologic features containing ductal and myoepithelial differentiation proven by IHC were included. Nine identified cases were submitted for p16 IHC and HR-HPV ISH. Results (if a Case Study enter NA) Patients ranged in age from 50 to 85. No cases resulted with positive HR-HPV, however all cases displayed staining for p16. All cases with benign breast tissue (6/9) exhibited some p16 positivity within luminal and myoepithelial cells. Conclusion HR-HPV ISH is a sensitive test; however, no cases were positive. Most tumors and benign breast expressed p16 in some form. p16 in basal-like breast cancer has been described, but only 3/7 cases with biomarkers were triple negative. Accordingly, p16 is not a reliable screening tool if detection of HPV becomes clinically relevant in the future. In this series, the phenotypic features assessed do not appear to be consistent harbingers of HPV infection. More studies are needed to assess the breast microbiome and oncogenic organisms to identify potential new therapeutic targets.