FDG PET in pulmonary sarcoidosis: An update and future aspects

Pulmonary sarcoidosis is a heterogeneous granulomatous disease with an unpredictable clinical course, in which accurate assessment of disease activity remains a major clinical challenge. Although up to two-thirds of newly diagnosed patients experience spontaneous remission, a significant proportion develop chronic or relapsing disease. Distinguishing self-limiting inflammation from progressive disease remains inherently difficult and has important therapeutic implications. 2-deoxy-2-[¹⁸F] fluoro-d-glucose (FDG) positron emission tomography/computed tomography (FDG-PET/CT) provides functional assessment of metabolic activity and has emerged as a valuable adjunct in sarcoidosis, with established utility in cardiac involvement and growing evidence supporting its role in pulmonary disease. This review examines the current evidence for the use of FDG-PET/CT in detecting active pulmonary inflammation, guiding biopsy, assessing multisystem involvement, and monitoring treatment response, and discusses its evolving integration into clinical care. We also highlight key limitations, including lack of standardized interpretation criteria, and variability in clinical decision-making. Finally, future directions are explored, with emphasis on imaging-based phenotyping, radiomics and artificial intelligence, quantitative and volumetric PET metrics, integration with clinical and serum biomarkers, and the need for prospective studies and evidence-based guidelines. Collectively, these developments position FDG-PET/CT as a promising tool for activity-based, personalized assessment of pulmonary sarcoidosis, while underscoring the need for further validation to support routine clinical adoption.