We report on a case of a 43-year-old woman with primary angiosarcoma of the left breast: She was admitted to the hospital complaining of a lump in her left breast. Physical examination revealed a large mass in the breast and an excisional biopsy was performed. The histopathological examination showed an angiosarcoma. The preoperative staging work-up did not show any evidence of metastasis and the patient underwent a left mastectomy. The tumour measured 8 cm in diameter and was excised on a tumour-free margin. Postoperatively, adjuvant local radiotherapy was delivered. Angiosarcoma of the breast is a rare condition with poor prognosis. Tumour size and the degree of tumour differentiation are the most important prognostic factors. Simple mastectomy is the generally recommended therapeutic option, while the role of adjuvant therapy remains to be evaluated.