Primary Breast Angiosarcoma
Grade III (high-grade) angiosarcomas are composed of anaplastic cells and often show solid growth pattern. Increased mitotic activity (including atypial forms), necrosis and focal hemorrhages (which create blood lakes) are common. The tumor cells have spindle or epithelioid phenotype, moderate to abundant eosinophilic or amphophilic cytoplasm with indistinct cytoplasmic borders, pleomorphic nuclei with clumped chromatin, and prominent nucleoli. The areas away from the tumor often show numerous vascular channels with capillary- or vein-like morphology infiltrating the breast parenchyma. These areas have benign appearance and resemble angioma/angiomatosis. As they approach the tumor, the vascular spaces coalesce into larger anastomosing channels lined by more atypical endothelium with tufting which merge with the solid tumor (as seen here).