[Two cases of radiotherapy-induced sarcoma after breast cancer surgery]

We report 2 cases of radiotherapy-induced sarcoma of the residual breast after breast cancer surgery. In 1 case, the patient was a 64-year-old woman. She underwent breast-conserving surgery and axillary lymph node dissection followed by irradiation to the residual breast in July 2001. A 1.1 × 1.0-cm tumor was noted in the residual breast 7 years 5 months after radiotherapy. An excisional biopsy was performed, and a histological diagnosis of angiosarcoma was made. She died of lung and peritoneal metastases 3 years 2 months after the diagnosis. In the other case, the patient was also 64 years old. She underwent breast-conserving surgery and sentinel lymph node biopsy followed by irradiation to the residual breast in October 2006. A 5.7 × 3.9-cm induration was noted in the residual breast 3 years 5 months after radiotherapy. A core needle biopsy was performed, and a histological diagnosis of sarcoma was made. Mastectomy was performed, and the histological diagnosis was malignant fibrous histiocytoma. She died of chest wall and intrapleural tumor recurrence 3 months after the mastectomy. Although radiotherapy-induced sarcoma is rare, early detection of the tumor in the irradiation area is important, as radiotherapy is often performed for breast cancer patients.