A 51-year-old Korean woman presented with a non-tender, well-demarcated, reddish, edematous patch on the right anterior chest where a previous mastectomy and radiation therapy had been performed. She had been diagnosed as having infiltrating ductal carcinoma of the right breast about 1 year ago. Histopathological findings of the skin lesions were consistent with inflammatory metastatic carcinoma of the breast. Inflammatory carcinoma or carcinoma erysipeloides is a well-established entity most frequently associated with carcinoma of the breast. It is characterized by dermal lymphatic invasion by malignancy and clinically should be distinguished from erysipelas or cellulitis. We describe a case of inflammatory metastatic carcinoma derived from an infiltrating ductal carcinoma of the breast which can be clinically confused with radiation dermatitis.