Breast carcinoma en cuirasse (CeC) is an extremely rare form of cutaneous metastases of breast cancer, characterized by diffuse sclerodermoid induration of the skin. It may be difficult to distinguish CeC from some skin diseases, including postirradiation morphea, inflammatory breast cancer, radiation dermatitis, and other cutaneous metastases, but it can be easily discerned by histology. Because of the small number of documented cases, the treatment consensus has not been clearly defined. Here, we show a 45-year-old woman with grade III infiltrating ductal carcinoma manifesting as CeC to the chest wall. Early diagnosis and treatment are essential to prevent the catastrophic natural progression of this rare malignancy.