A 75-year-old woman had suffered from lymphedema of the left upper extremity for 7 years after undergoing a radical mastectomy with lymph node dissection followed by radiation treatment for the left breast cancer. She visited our hospital with a solitary reddish nodule which measured 6 × 5 × 3 cm. Histological findings of the nodule revealed numerous spindle shaped cells with marked cellular atypia forming slit-like spaces, confirming the diagnosis of Stewart-Treves syndrome. The tumor was surgically resected with wide free margin and treated with radiation therapy. No local recurrence or metastasis has been seen for 34 months after the resection.[Skin Cancer (Japan) 2012 ; 27 : 191-194]