Abstract
Myofibroblastic sarcomas of the breast are rare, leading to very few reports on their prognosis and metastasis potential. We report a case of lung metastasis from a mammary low-grade myofibroblastic sarcoma. A 55-year-old woman with no remarkable past medical history presented to a local clinic with a palpable mass in her left breast that had persisted for 3 weeks. Vacuum-assisted excisional biopsy initially suggested a diagnosis of a malignant phyllodes tumor. Subsequent wide excision with clear surgical margins led to a confirmed diagnosis of myofibroblastic sarcoma. No additional treatments, such as chemotherapy or radiotherapy, were administered. Four years later, lung metastases were detected on chest computed tomography. The patient subsequently underwent wedge resection of the lung. Three years later, metastasis to the cervical lymph nodes was discovered. Owing to tumor emboli, the patient ultimately died from brain infarction. No consensus guidelines for standard treatment exist due to the scarcity of the disease. Although surgical resection remains the most reasonable treatment option, additional therapies should be considered to reduce the risk of metastatic spread to other organs.