Spontaneous Regression of Locally Advanced Breast Cancer Following Cardiopulmonary Arrest: A Case Report

Spontaneous regression in breast cancer is rare but can dramatically improve patient prognosis. Although the underlying mechanism is unknown, it may be due to a biological response to external invasion. An 81-year-old woman presented to our emergency department with a 600x100mm large breast mass. Five days after the emergency room visit, she lost consciousness bleeding from the breast mass. She experienced cardiopulmonary arrest (CPA), and after 10 minutes of cardiopulmonary resuscitation, the patient underwent a return of spontaneous circulation (ROSC). She was diagnosed with hemorrhagic and cardiogenic shock, and the breast mass gradually collapsed on the 17th day. Twelve months after CPA, the patient underwent left mastectomy and axillary lymph node dissection (II) for left breast cancer. Postoperatively, the patient continued to receive aromatase inhibitors and radiation therapy and she did not experience any recurrence two years after surgery. Spontaneous regression of breast cancer following CPA has not been previously reported, and, to the best of our knowledge, this case report is the first. We hypothesized that the tumor might have had relative ischemia and internal necrosis due to the blockage of the nutrient artery.