Myxofibrosarcoma that Developed Rapidly in the Breast of an Elderly Man and Recurred Early after Surgery: A Case Report.

BACKGROUND Myxofibrosarcoma is a rare disease occurring subcutaneously in the limbs. We report a case of a rapidly growing myxofibrosarcoma in the breast of an elderly man that recurred early after surgery. CASE PRESENTATION A 73-year-old man presented with a breast mass. Physical findings showed a large tumor in the right breast, and malignancy was suspected on ultrasonography. Computed tomography (CT) revealed tumor invasion into the pectoralis major and pectoralis minor muscles. Positron emission tomography/CT showed no abnormality in other organs. Needle biopsy results excluded breast cancer but did not provide a definitive diagnosis. However, the tumor grew rapidly before further results were available, so emergency mastectomy was performed. The final pathological diagnosis was high-grade myxofibrosarcoma. Postoperative radiotherapy was started because of remnant tumor. The wound became worsened and swollen, and needle biopsy 10 days after the start of therapy indicated recurrence. Radical resection and thoracoplasty were performed. Postoperative pathological specimens showed no residual tumor. Radical radiation therapy was resumed. The patient has shown no recurrence after an year. CONCLUSIONS It is important to consult a soft tissue oncologist for tumors in the breast and perform appropriate examination and treatment if soft tissue tumors cannot be ruled out.