Clinicopathologic characteristics of early-onset breast cancer among unselected young Black women.

Black women are more likely to develop and die from early-onset breast cancer. Hereditary breast cancer (HBC) is strongly associated with early age of onset. Accordingly, HBC characteristics in young Black women were evaluated. Black women diagnosed with invasive breast cancer at age 50 years or younger between 2005 and 2018 were recruited through the state cancer registries in Florida and Tennessee. Participants were asked to complete a questionnaire, sign medical records releases, and donate a saliva sample for free genetic testing to identify HBC germline pathogenic or likely pathogenic variant (GPV). Women with sporadic versus hereditary breast cancer were compared, based on age distribution, clinical characteristics, and family cancer history. Among 686 participants with confirmed genetic testing, 15.3% had GPVs in breast and/or ovarian cancer predisposition genes, including BRCA1 (7.7%), BRCA2 (4.5%), PALB2 (0.9%), and ATM (0.7%), with 1.5% in other genes. Compared to the sporadic group, triple-negative breast cancers were overrepresented among BRCA1 carriers (23.6% vs. 75.5%; p < .001), and family history of breast cancer was significantly more frequent among BRCA1, BRCA2, and PALB2 carriers (all p < .05). The majority of breast cancers occurred by age 40 years in BRCA1 carriers (52.8%), compared to other genes, where age was more evenly distributed. Among unselected young Black women with breast cancer, our findings demonstrate that the highest frequency of HBC GPVs are in BRCA1, BRCA2, and PALB2, with identification of distinct histopathologic and demographic characteristics across HBC genes, underscoring the critical need for genetic testing in all populations.