[en] The Stewart-Treves Syndrome is defined as an angiosarcoma (very aggressive malignant tumor originating from endothelial cells) appearing in a specific clinical setting. This tumor develops in patients suffering from chronic lymphedema of the upper limb following mastectomy and axillary lymph node dissection for breast cancer. The diagnosis relies on medical history, clinical examination and a histological assesment (biopsy or resection). This syndrome represents a rare clinical entity. Unfortunately, the prognosis is poor. A large surgical resection is the treatment of choice if the patient is a candidate for a surgical resection with a curative intent Radiotherapy is sometimes used as a palliative local treatment. Chemotherapy is only used in more advanced cases, not curable by surgery alone.