Is focal fatty infiltration of the liver (FFI) a benign condition?

Focal Fatty Infiltration of the Liver: A Benign Condition

Focal fatty infiltration (FFI) of the liver is a benign condition that does not require specific treatment or intervention. 1 According to the American Association for the Study of Liver Diseases (AASLD) guidelines, focal fatty infiltration is explicitly classified as a benign hepatic mass lesion, distinct from malignant conditions such as hepatocellular carcinoma, cholangiocarcinoma, or metastatic disease 1.

Characteristics and Diagnosis

Focal fatty infiltration is characterized by:

• Areas of fat deposition in specific regions of the liver
• Typically occurs adjacent to anatomical landmarks such as the falciform ligament, gallbladder fossa, or porta hepatis 2
• No mass effect in most cases, though rare cases with mass effect have been reported 3
• Often geometric or ovoid low-attenuation areas on CT imaging 2

Imaging Features

Ultrasound findings:

• Areas of increased echogenicity compared to surrounding liver parenchyma
• No displacement of blood vessels (vessels pass through the lesion undisturbed)
• No capsule or mass effect in typical cases

MRI findings:

• Signal drop on opposed-phase compared to in-phase T1-weighted images
• No enhancement pattern suggestive of malignancy
• No restricted diffusion

Differentiation from Malignancy

Several features help distinguish focal fatty infiltration from malignant lesions:

• Geographic rather than rounded borders
• Absence of mass effect on surrounding structures in most cases
• No vascular invasion or displacement
• Typical locations adjacent to anatomical landmarks
• Signal characteristics on MRI consistent with fat content

Clinical Significance

The American College of Radiology (ACR) and AASLD guidelines indicate that:

• Focal fatty infiltration does not require biopsy when typical imaging features are present 1
• It does not progress to malignancy
• It may resolve with lifestyle modifications including weight loss, exercise, and alcohol abstinence 4

Management Approach

For typical focal fatty infiltration:

1. No specific treatment is required for the lesion itself
2. Address underlying causes (if present):
   • Weight loss for obesity-related fatty liver
   • Alcohol cessation if alcohol-related
   • Management of metabolic syndrome components
3. Follow-up imaging is generally not necessary if the diagnosis is confident

Potential Pitfalls

• Atypical appearances of focal fatty infiltration can mimic malignancy 5, 6
• Multiple focal fatty lesions may be confused with metastatic disease 6
• In rare cases, focal fatty infiltration can present with mass effect, making differentiation from tumors challenging 3

When imaging findings are atypical or concerning, additional imaging with MRI is preferred over biopsy as the next step, as MRI can reliably distinguish fat-containing lesions from true neoplasms 7.

In conclusion, focal fatty infiltration of the liver is a benign condition that can be confidently diagnosed with appropriate imaging techniques and does not require specific treatment or intervention beyond addressing any underlying causes of fatty liver disease.