Are the majority of breast and ovarian cancer cases attributed to inherited mutations in BRCA1 or BRCA2 genes?

The majority of breast and ovarian cancer cases are not attributed to inherited mutations in the BRCA1 or BRCA2 genes. While these two genes are indeed significant contributors to hereditary breast and ovarian cancer syndromes—accounting for a substantial proportion of familial cases—they only represent a fraction of the overall incidence of these cancers. Many cases of breast and ovarian cancer occur sporadically, without any known inherited genetic mutation. The majority of breast cancer cases do not involve BRCA mutations at all, and while BRCA mutations significantly increase the risk of developing these cancers, they are not the sole factor and affect only a subset of patients.

Inherited mutations in BRCA1 and BRCA2 account for approximately 5-10% of breast cancer cases and about 10-15% of ovarian cancer cases. Thus, while their importance cannot be understated, the answer highlights that the majority of cases arise from other genetic, environmental, and lifestyle factors, not exclusively from BRCA mutations. This distinction is critical for understanding the broader landscape of cancer risk and the multifactorial nature of these diseases.