18 F-FDG PET/CT in Disseminated Cryptococcosis Mimicking Malignancy With Rib Osteolysis and Chest Wall Invasion.

Disseminated cryptococcosis is a rare systemic fungal infection that can mimic thoracic malignancies. We report a 56-year-old man with known cryptococcosis on antifungal therapy who underwent 18 F-FDG PET/CT for response evaluation. Imaging revealed a heterogeneously FDG-avid pleural-based right upper lobe mass with lytic destruction of the first and second ribs and extension into chest wall musculature, with pulmonary nodules and nodal disease. Interval imaging demonstrated metabolic regression of adrenal and pulmonary lesions. This case highlights the diagnostic challenge of cryptococcosis presenting as an aggressive pseudotumor and underscores the utility of 18 F-FDG PET/CT in disease characterization and therapeutic monitoring.