FDG-Avid Benign Disease: Infection and Inflammation Mimics

C. Infection and inflammation (including sarcoidosis, tuberculosis, fungal infections, post-surgical healing) — inflammatory cells are highly FDG-avid

FDG (fluorodeoxyglucose) is a glucose analogue taken up by any metabolically active cell — not just cancer cells. Activated macrophages, neutrophils, and other inflammatory cells have dramatically upregulated glucose metabolism and can show very intense FDG uptake indistinguishable from malignancy. Common causes of false-positive FDG uptake include: sarcoidosis (classic pitfall in lymphoma); granulomatous infections (TB, histoplasmosis); post-surgical/radiation inflammation; brown fat (supraclavicular/mediastinal); healing fractures; inflammatory bowel disease. Correlating with CT morphology, clinical history, and if needed biopsy is essential to avoid misinterpreting FDG-avid inflammation as tumor recurrence.