Spontaneous regression of breast angiosarcoma after conservative treatment with radiotherapy: a case report and review of the literature.

Angiosarcoma of the breast is a rare disease, and approximately 1 % of all affected patients are treated with breast-conserving therapy (BCT) and radiotherapy (RT) for primary breast cancer. The prognosis for this tumor is quite dismal, with high rates of recurrence and poor overall survival. This report presents the case of a 73-year-old female who underwent BCT followed by RT for left breast carcinoma 18 years previously. The patient visited the hospital with a complaint of a new mass in the left breast. The lesion initially decreased in size; however, it subsequently began to rapidly enlarge. A core needle biopsy of the mass was performed under ultrasonography, with a diagnosis of a spindle cell sarcoma, most conceivably an angiosarcoma, originating from the left breast, suspected to be induced by RT. The tumor was resected with the surrounding skin, and immunohistochemically diagnosed as angiosarcoma of the left breast, without evidence of breast cancer in any lesion, suggesting that RT induced the tumor formation. We herein report this rare case and the ultrasound imaging findings.