Metabolically Silent Diffuse Hepatic Involvement in Multiple Myeloma: An ¹⁸F-FDG-PET/CT Pitfall

Diffuse hepatic involvement in multiple myeloma is rare and may present a diagnostic challenge ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT). We present the case of a 59-year-old man with a 3-year history of multiple myeloma who developed progressive hepatomegaly and perihepatic ascites. ¹⁸F-FDG PET/CT demonstrated marked diffuse liver enlargement without any focal or diffuse hepatic 18F-FDG uptake, while mild diffuse skeletal uptake suggested a globally ¹⁸F-FDG-low myeloma phenotype. Given the discordance between severe morphological findings and the absence of hepatic metabolic activity, a liver biopsy was performed, which revealed diffuse sinusoidal infiltration by CD138-positive, lambda-restricted plasma cells and excluded hepatic amyloidosis. Following systemic therapy, hepatomegaly and ascites regressed, while hepatic ¹⁸F-FDG uptake remained absent. Written informed consent for publication was obtained from the patient. This case highlights an important limitation of ¹⁸F-FDG PET/CT in detecting diffuse hepatic myeloma and emphasizes the need for multimodal diagnostic integration.