Our patient was a 36-year-old female diagnosed with Grade II ER+/PR-/Her-2 - ductal carcinoma in situ (DCIS) in the left breast. She underwent left lumpectomy and received treatment with tamoxifen and radiotherapy. Three years later, she presented with multiple diffused skin nodules on the chest and upper left arm. 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) exam showed widespread metastasis in the chest, upper left arm, left axillary lymph nodes, and left suprascapular muscle. FDG-PET/CT imaging of breast carcinoma en cuirasse is very rare. FDG-PET/CT is useful in detecting recurrent breast cancer.