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

Area of Science:

• Orthopedics
• Nuclear Medicine
• Toxicology

Background:

• A 76-year-old woman presented with a skin lesion requiring characterization and staging.
• Initial assessment involved [18F]FDG PET/CT due to suspicion of malignancy.
• The patient had a history of a left shoulder prosthesis implanted 2.5 years prior.

Purpose of the Study:

• To characterize and stage a suspicious skin lesion.
• To investigate abnormal findings associated with a left shoulder prosthesis.
• To diagnose the underlying cause of systemic symptoms potentially related to the prosthesis.

Main Methods:

• [18F]FDG PET/CT imaging for lesion characterization and staging.
• CT imaging to assess the left shoulder prosthesis.
• Histopathologic analysis of liver lesion biopsies.
• Surgical removal of the prosthesis and analysis of periprosthetic samples.
• Blood metal ion analysis (titanium and nickel).

Main Results:

• [18F]FDG PET/CT showed uptake in the skin lesion, periprosthetic tissues, lymph nodes, and liver lesions.
• CT revealed loosening of the left shoulder prosthesis.
• Liver biopsies indicated epithelioid giant cell granulomas.
• Periprosthetic samples showed inflammation but no microbial growth.
• Blood analysis revealed markedly elevated titanium and nickel levels.

Conclusions:

• The findings established a diagnosis of systemic metallosis.
• Elevated metal ion levels were linked to the prosthetic material.
• Systemic metallosis should be considered in patients with prosthetic implants and unexplained systemic or localized findings.