A 65-year-old man presented to the dermatology clinic with a 7-month history of painless skin thickening over the left side of his chest and on his left arm. On physical examination, the skin on the left side of the chest and on the left nipple was sclerotic. Multiple erythematous nodules were observed on the left arm, axilla, and posterior trunk, and lymphedema in the left arm and left axillary lymphadenopathy were present. A skin-biopsy specimen from the chest showed metastatic carcinoma that was strongly suggestive of a primary breast cancer, without expression of hormone receptors or human epidermal growth factor receptor 2. The patient’s skin findings were attributed to carcinoma en cuirasse, a rare form of cutaneous breast cancer metastasis that results in extensive fibrosis of the skin and subcutaneous tissues of the chest wall. The name derives from the resemblance of the condition to a breastplate of armor. The patient was referred to the oncology clinic, and combined positron-emission tomography and computed tomography revealed diffuse 18F-fluorodeoxyglucose–avid stranding in the subcutaneous soft tissue of the left chest wall, as well as involvement of the left axillary lymph nodes and bones. Palliative chemotherapy was administered.