Imaging Pearls ❯ Liver ❯ Fat in Tumors
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- “Gross fat at CT is less attenuating than other soft tissues, measuring −20 HU or less. The presence of intravoxel fat on CT will reduce the attenuation of that tissue; for example, fatty livers show progressively lower hepatic attenuation values that correspond to worsening grades of steatosis. On unenhanced CT, fat-containing liver lesions are hypoattenuating to liver, provided there is no steatosis; however, fat attenuation values are measured only when fat is present in sufficient quantity.”
Fat-Containing Liver Lesions on Imaging: Detection and Differential Diagnosis Andreu F. Costa et al. AJR 2018; 210:68–77 - Fat Containing Hepatic Tumors: Differential Dx
• Hepatocellular Carcinoma and Regenerative Nodules
• Hepatocellular Adenoma
• Focal Nodular Hyperplasia
• Angiomyolipoma
• Lipoma
• Fat-Containing Metastases of an Extrahepatic Primary Tumor
• Hydatid Cyst - “Hepatic AMLs are typically solitary but often coexist with renal AMLs when associated with the tuberous sclerosis complex. Although 20% of renal AMLs are associated with tuberous sclerosis complex, hepatic AMLs are associated with tuberous sclerosis complex in only 6–10% of cases.”
Fat-Containing Liver Lesions on Imaging: Detection and Differential Diagnosis Andreu F. Costa et al. AJR 2018; 210:68–77 - “True hepatic lipomas are less common than AMLs. Because they are composed entirely of mature adipose tissue, they are homogeneously echogenic on ultrasound and may exhibit posterior acoustic attenuation . Pure fat attenuation of −20 HU or less is measured on CT. On MRI, lipomas are isointense to subcutaneous fat on all sequences, with homogeneous loss of signal noted on fat-saturated images, and they are circumscribed by etching artifact on opposed-phase GRE T1-weighted MRI. There is little to no enhancement on CT or MRI.” Fat-Containing Liver Lesions on Imaging: Detection and Differential Diagnosis Andreu F. Costa et al. AJR 2018; 210:68–77
- “Fat-containing liver metastases are uncommon and typically arise from liposarcomas and malignant germ cell tumors. Although clear cell renal cell carcinoma (RCC) likely is the most common fat-containing primary malignancy to metastasize to the liver, only a minority of clear cell RCC metastases show fat signal on chemical-shift MRI. The primary diagnosis is often known at the time of presentation with liver metastases; fat-containing liver metastases also typically occur in the setting of widespread metastatic disease, with multifocal hepatic and extrahepatic metastases.”
Fat-Containing Liver Lesions on Imaging: Detection and Differential Diagnosis Andreu F. Costa et al. AJR 2018; 210:68–77 - “When present, fat droplets or a fat-fluid level within a liver lesion distinguish hydatid disease from other fat-containing liver lesions. Other imaging features of hydatid disease will depend on the evolutionary stage of the cyst, as outlined by the World Health Organization classification scheme. These features include intraluminal debris corresponding to hydatid sand (the snow flake sign); multivesicular, multiseptated lesions in which daughter cysts partly or completely fill the mother cyst, resembling a honeycomb; detached membranes (the water lily sign); and rim calcification.”
Fat-Containing Liver Lesions on Imaging: Detection and Differential Diagnosis Andreu F. Costa et al. AJR 2018; 210:68–77