HER-2 overexpressing breast cancer during pregnancy: a case report and literature review.

[BACKGROUND] Breast cancer during pregnancy (PrBC) is rare but increasingly reported due to delayed childbearing, widespread assisted reproduction, and younger onset of breast cancer. Among these, HER2-overexpressing subtypes pose particular clinical challenges in balancing effective oncologic control with fetal safety. It requires a delicate balance between optimizing maternal oncologic outcomes and ensuring fetal safety.

[CASE PRESENTATION] We report the case of a 33-year-old woman diagnosed with HER-2 overexpressing invasive ductal carcinoma of the right breast at 16 weeks of gestation. Driven by a strong desire to continue the pregnancy, the patient, in consultation with a multidisciplinary team, opted for neoadjuvant chemotherapy. From 17 to 31 weeks' gestation, she received four cycles of epirubicin and cyclophosphamide, followed by one cycle of nab-paclitaxel, achieving a partial response. At 37 weeks, she underwent a successful vaginal delivery, giving birth to a healthy female infant. Postpartum, she continued her neoadjuvant treatment with three cycles of nab-paclitaxel plus dual anti-HER2 therapy (trastuzumab and pertuzumab). After completing the full neoadjuvant regimen, she underwent breast-conserving surgery, and pathology confirmed a complete response. Her postoperative treatment included adjuvant dual anti-HER2 therapy and whole-breast radiotherapy. At the last follow-up (18 months post-delivery), the mother showed no signs of recurrence, and the child exhibited normal growth and neurodevelopment.

[CONCLUSIONS] This case demonstrates that with careful multidisciplinary planning and individualized treatment strategies, it is feasible to achieve both successful maternal oncologic control and the delivery of a healthy baby in patients with HER-2 overexpressing breast cancer during pregnancy. This case contributes valuable evidence to the management of this complex clinical scenario.