[Radiation-Induced Undifferentiated Pleomorphic Sarcoma after Breast-Conserving Surgery-A Case Report].

The patient was a 73-year-old woman who had undergone breast-conserving surgery followed by irradiation (50 Gy/25 Fr)to the residual breast for left breast cancer 4 years before. Computed tomography for routine examination revealed a soft tissue mass on her left chest wall. Ultrasonography showed a hypoechoic mass with heterogeneous internal echo, 3.5×3.0×1.5 cm in size. Core-needle biopsy was performed, and histological examination revealed proliferation of spindle-shaped or pleomorphic and highly atypical cells. On immunohistochemistry, the tumor was negative for AE1/AE3, CD34, SMA, desmin, and S-100 and focally positive for CD68. Based on these findings, undifferentiated sarcoma was suspected. The patient underwent wide local excision of the chest wall with a surgical margin of 3-4 cm from the tumor edge. The histological diagnosis was undifferentiated pleomorphic sarcoma. Judging from the clinical course, this tumor was radiation-induced sarcoma. The patient remains disease-free 54 months after the operation.