[18F]FDG PET/CT revealing extensive cutaneous involvement in Sézary syndrome

Sézary syndrome is a rare cutaneous T-cell lymphoma characterized by erythroderma and circulating malignant T cells. This study presents the case of a 31-year-old man with extensive skin involvement detected by 2-deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography/computed tomography ([¹⁸F]FDG PET/CT), demonstrating widespread hypermetabolic lesions across the body. In contrast to computed tomography (CT) or magnetic resonance imaging (MRI), which may overlook subtle or millimetric cutaneous lesions, [¹⁸F]FDG PET/CT accurately delineated the extent of disease and provided critical information for staging, therapeutic decision-making, and response assessment. This case underscores the clinical value of [¹⁸F]FDG PET/CT in evaluating extensive cutaneous involvement in Sézary syndrome.