What type of cancer is most commonly seen in females with BRCA1-related HBOC?

In females with BRCA1-related hereditary breast and ovarian cancer (HBOC), breast cancer is the most commonly observed malignancy. This association stems from the significant role that BRCA1 plays in DNA repair processes, specifically in the repair of double-strand breaks. When BRCA1 is mutated, the ability to repair damaged DNA is compromised, increasing the risk of cancer development, particularly in breast and ovarian tissues.

Studies indicate that women with BRCA1 mutations have a markedly higher lifetime risk of developing breast cancer, often estimated to be as high as 70% to 80%. Ovarian cancer is also a serious risk, but the prevalence of breast cancer in this population remains higher when considering the broader spectrum of HBOC manifestations. Additionally, while endometrial and thyroid cancers can occur in individuals with BRCA mutations, they are not the primary cancers associated with BRCA1. Therefore, breast cancer is the most prevalent cancer in females with BRCA1-related HBOC.