Breast pseudoaneurysm after core needle biopsy in a pregnant patient

Breast pseudoaneurysm is an extremely rare complication of interventional breast procedures. Pregnancy and lactation are associated with increased breast vascularization, which may act as a risk factor. We present the case of a 36-year-old woman in the third trimester of a spontaneous twin pregnancy, who presented with a newly-detected BI-RADS 4 mass in her right breast. The patient requested not to defer a biopsy until after the pregnancy, and an ultrasound-guided breast core biopsy was performed. The patient presented bleeding during the procedure, but no hematomas or other vascular lesions were immediately detected. During follow-up, a breast ultrasound revealed an anechoic circumscribed mass and high-velocity blood flow. The color Doppler showed a spiral blood flow with the Yin-Yang sign, together with a communication channel between the sac and feeding artery. A diagnosis of breast pseudoaneurysm was made. The patient was managed conservatively, and breastfeeding continued normally. This case report highlights the importance of color Doppler in the detection of pseudoaneurysms, and the need to consider deferring invasive breast procedures in pregnant women when possible.