Abstract
INTRODUCTION AND IMPORTANCE: Undifferentiated pleomorphic sarcoma (UPS), also known as malignant fibrous histiocytoma, is a rare mesenchymal tumor that occurs mostly in the soft tissue of the limbs and retroperitoneum. UPS of the breast is extremely rare, with less than 20 cases reported in the literature. CASE PRESENTATION: We present a case of UPS of the right breast in a 56-year-old female. The growth of tumor could not be impeded by chemotherapy and radiotherapy. Then, she underwent right modified radical mastectomy with axillary lymph node dissection. The patient died eventually due to severe respiratory failure. UPS of the breast is a rare and aggressive tumor that presents with a rapidly growing mass. It can be difficult to diagnose as it shows no specific histological features and can mimic other spindle cell tumors of the breast. CLINICAL DISCUSSION: Breast sarcomas are categorized in very rare malignancies, and the mortality of this type of cancers are significantly high as they often are not diagnosed in early stages. CONCLUSION: The treatment of UPS of the breast is mostly surgical, with adjuvant radiotherapy and chemotherapy depending on the tumor characteristics and response to neoadjuvant chemotherapy. Long-term follow-up is necessary as these tumors have a high rate of local recurrence and distant metastasis.