An advanced, invasive breast adenocarcinoma characterized by the presence of distinct changes in the overlying skin. These changes include diffuse erythema, edema, peau d''orange (skin of an orange) appearance, tenderness, induration, warmth, enlargement, and in some cases a palpable mass. The skin changes are the consequence of lymphatic obstruction from the underlying invasive breast adenocarcinoma. Microscopically, the dermal lymphatics show prominent infiltration by malignant cells. The invasive breast adenocarcinoma is usually of ductal, NOS type. There is not significant inflammatory cell infiltrate present, despite the name of this carcinoma. [from
NCI]