Pseudoaneurysm of the Breast after Diagnostic Core-Needle Biopsy: Contextualizing Impact on Treatment

This case report considers an iatrogenic pseudoaneurysm (PSA), a rare event occurring in fewer than 2% of patients, after a core-needle biopsy of the breast in a 46-year-old with stage IIIC triple negative invasive breast carcinoma on preoperative chemoimmunotherapy with the PD-1 inhibitor pembrolizumab. A post-biopsy MRI (magnetic resonance imaging) demonstrated a well-defined, contrast-enhancing lesion with pulsatile flow consistent with PSA. Multidisciplinary discussions addressed PSA management and timing of immunotherapy, given the potential association of PD-1/PD-L1 inhibitors with the progression of vascular anomalies. Although breast PSA is uncommon, this complication warrants investigation in light of the increasing application of immunotherapies, which may mediate vascular inflammation.