Clinical History: This post-radiation angiosarcoma of breast (images 41-43) is from a 58 y/o female with invasive ductal carcinoma of breast. She had undergone neoadjuvant chemotherapy and partial mastectomy followed by radiation therapy. She presented with a mass in the same breast seven years later and underwent radical mastectomy after a core biopsy. The mastectomy specimen showed a large ill-defined hemorrhagic mass surrounded by several red-purple nodules. Histologically, it was composed of a poorly-differentiated malignant tumor consisting of solid sheets of epithelioid cells as well as slit like spaces lined by highly atypical cells with large vesicular nuclei and prominent nucleoli. The tumor cells were strongly positive for CD31 and CD34 and negative for cytokeratin AE1/AE3. The final diagnosis was: Post-radiation Epithelioid Angiosarcoma.