Medullary Carcinoma : Tumor borders
High magnification view of tumor border in a medullary carcinoma of the breast. Grossly and microscopically, the tumor had well-circumscribed, rounded, smooth borders. The carcinoma was confined to the syncytial clusters within the lympho-plasmacytic reaction. A few lymphocytes and plasma cells (but no tumor cells) are seen infiltrating the fat beyond the main tumor.