Fat necrosis in the breast from methylene blue dye injection.

Sentinel lymph node biopsy has become the standard of clinical care in staging axillary lymph nodes for breast carcinoma. While deemed safe and effective, methylene blue dye has been associated with infection, fibrosis, and skin and fat necrosis. The variable appearance of surgical dye-related fibrosis and fat necrosis on imaging studies poses a challenge to both radiologists and clinicians. We present a patient in whom a new enhancing lesion was visualized on follow-up magnetic resonance imaging for known breast carcinoma in the setting of neoadjuvant chemotherapy.