Case Report: A case of a pregnancy-associated breast cancer patient with a pathogenic variant in BRCA1 who underwent staged risk-reducing salpingo-oophorectomy and contralateral risk-reducing mastectomy.

Pregnancy-associated breast cancer in patients with hereditary breast and ovarian cancer syndrome (HBOC) is relatively rare, and reports on treatment outcomes, including those involving risk-reducing surgery, remain limited. A 38-year-old woman at 8 weeks' gestation presented with a palpable mass in the left breast. Imaging revealed a tumor in the left breast, and further evaluation led to a diagnosis of luminal B-like, stage IIA left breast cancer. Her family history included a paternal cousin with pregnancy-associated breast cancer at age 37, a maternal grandmother with ovarian cancer at age 68, and a maternal grandaunt with breast cancer. BRCA1/2 genetic testing identified a pathogenic variant in BRCA1. The patient had previously lost her fourth child due to a fetal anomaly (anencephaly) during pregnancy and strongly wished to continue her current pregnancy with her fifth child. Given that neoadjuvant chemotherapy would not affect the surgical approach, that only anthracycline-based therapy can be administered during pregnancy, and that postoperative adjuvant therapy would not be significantly impacted, as well as the potential fetal risks associated with prolonged general anesthesia, contralateral risk-reducing mastectomy (CRRM) was deferred until after delivery. Left total mastectomy with sentinel lymph node biopsy was performed first. As postoperative adjuvant therapy, she received four cycles of doxorubicin and cyclophosphamide during pregnancy, followed by four cycles of docetaxel after delivery, along with tamoxifen and tegafur-gimeracil-oteracil potassium. She underwent staged risk-reducing salpingo-oophorectomy and CRRM after surgery for left breast cancer. Even in pregnancy-associated breast cancer complicated by HBOC, management should be individualized with careful consideration of safety, and the timing of each intervention should be determined according to the specific clinical circumstances of each patient.