Subcutaneous Staining of the Breast from Superparamagnetic Iron Oxide Nanoparticle Tracer Injection.

This article focuses on the clinical and imaging findings related to retained superparamagnetic iron oxide (SPIO) nanoparticles used for sentinel lymph node mapping in breast cancer surgery. It presents a case of a 65-year-old woman with periareolar skin discoloration following lumpectomy and sentinel lymph node biopsy, attributed to SPIO tracer retention. The retained SPIO particles caused skin discoloration and susceptibility artifact on breast MRI, limiting evaluation of the regional breast tissue, while mammography and ultrasound showed benign postoperative changes without corresponding abnormalities. The article emphasizes the importance for breast radiologists to recognize SPIO-related imaging features to differentiate them from pathological mimics and suggests contrast-enhanced mammography as an alternative imaging modality when MRI is compromised.