The Association Between Breast Cancer Predisposing Genetic Variants and Multifocal, Multicentric Breast Cancer.

Breast-conserving surgery is often discouraged in BRCA gene carriers with early onset breast cancer. The genetic variant carrier breast cancers are more likely to be multifocal or multicentric (MFMC). This retrospective study includes newly diagnosed patients with breast cancer undergoing genetic testing between 2010 and 2021 within the Johns Hopkins Regional Health System. After excluding patients who received neoadjuvant chemotherapy or stage IV breast cancers, patients were divided into two groups: those who tested positive for a variant recognized by the National Comprehensive Cancer Network as predisposing the patient to breast cancer (ATM, BRCA1, BRCA2, CHEK2, NF1, PALB2, RAD51C, RAD51D, and TP53) and those who tested negative. Pathologic features of the tumors were compared, focusing on evidence for MFMC disease, defined as more than one malignant foci more than 5 mm apart. Among the 282 eligible cases, 69 (24%) were positive for a genetic variant. The variant carriers were younger at diagnosis (p < 0.001), more likely to have invasive ductal carcinoma (p = 0.03), more likely to have undergone mastectomy (p = 0.03), and more likely to have a grade 3 cancer (p = 0.003). Variant carriers were not more likely to have MFMC disease (28% vs. 22%, p = 0.4). A positive genetic variant was not a predictor of MFMC within the entire cohort [odds ratio (OR):1.3, 95% confidence interval (CI) 0.6-2.6, p = 0.5). Genetic variant carrier cancers are not more likely to be MCMF than sporadic cancers.