Steward-Treves syndrome is a cutaneous angiosarcoma that usually appears after long evolution of a lymphoedema after mastectomy for mammary neoplasia associated with an axillary dissection. This is a rare disease develop most of the time in upper arm and often confounded with cutaneous metastasis. Only the biopsy and immunohistochemical study confirm the diagnosis. The treatment is surgical and consists of large cutaneous excision, an amputation of the limb or even its disarticulation and will be followed by chemotherapy. Despite the treatment, the prognosis remains severe with poor survival. We report the case of a patient who had a Steward-Treves syndrome 20 years after lymphoedema following a left mastectomy with axillary dissection.