Systemic Metallosis Mimicking Malignancy on [18F]FDG PET/CT.

A 76-year-old woman was referred to perform a [18F]FDG PET/CT for characterization and staging of a skin lesion in the left posterior shoulder region suspected to be malignant. PET/CT images revealed [18F]FDG uptake of the skin lesion, peripheral soft tissues of a left shoulder prosthesis involving axillary region, left axillary and abdominal para-aortic enlarged lymph nodes, and 2 liver lesions. CT images exhibited loosening of the left shoulder prosthesis, which had been implanted approximately two and a half years before. Histopathologic analysis of liver lesions biopsies showed epithelioid giant cell granulomas. Surgery was performed for prosthesis removal. Analysis of periprosthetic samples performed during surgery revealed negative microbiological cultures and an inflammatory reaction with multinucleated giant cells. Metal ion analysis performed on blood samples showed markedly titanium and nickel elevated levels, establishing the diagnosis of systemic metallosis.