What is the recommended approach to evaluate and manage a newly identified liver lesion?

Evaluation and Management of Newly Identified Liver Lesions

The recommended approach to a newly identified liver lesion begins with risk stratification based on three clinical contexts—normal liver, known extrahepatic malignancy, or chronic liver disease/cirrhosis—followed by multiphasic contrast-enhanced MRI as the preferred imaging modality for lesions >1 cm, which establishes a definitive diagnosis in 95% of cases. 1, 2

Initial Risk Stratification

The evaluation pathway depends critically on patient risk factors and clinical context:

• Normal liver (no known malignancy or chronic liver disease): Benign lesions such as hemangioma, cysts, and focal nodular hyperplasia occur in up to 15% of the general population and represent the most likely diagnosis 1, 2, 3

• Known extrahepatic malignancy: Metastatic disease must be excluded, though benign lesions still occur in nearly 30% of cancer patients 1, 2, 3

• Chronic liver disease/cirrhosis: Hepatocellular carcinoma becomes the primary concern for lesions ≥10 mm, particularly when AFP is elevated and lesions are >2 cm 2, 3

Imaging Strategy by Lesion Size and Clinical Context

Lesions >1 cm in Normal Liver Patients

For indeterminate lesions discovered on ultrasound, noncontrast CT, or single-phase CT:

• First-line options (all equivalent): Multiphasic contrast-enhanced MRI (with and without IV contrast), multiphase contrast-enhanced CT, or contrast-enhanced ultrasound (CEUS) 1, 2, 3

• MRI superiority: MRI with contrast establishes a definitive diagnosis in 95% of liver lesions, significantly higher than CT, and only 1.5% require further imaging versus 10% with CT 1, 2

• Gadoxetate-enhanced MRI accuracy: 95-99% for hemangioma, 88-99% for focal nodular hyperplasia, and 97% for hepatocellular carcinoma 1, 2

• CEUS performance: Reaches a specific diagnosis in 83% of indeterminate lesions, distinguishes benign from malignant in 90% of cases, and correctly characterizes 90% of hemangiomas and 90% of focal nodular hyperplasia 1, 2, 3

• Multiphase CT requirements: Must include arterial and portal venous phases at minimum, with 2.5-5 mm slice thickness for optimal lesion characterization 3

Lesions >1 cm in Patients with Known Malignancy

• Preferred imaging: MRI with and without IV contrast or multiphase contrast-enhanced CT 1, 2, 3

• FDG-PET/CT role: Equivalent option when the lesion was initially found on noncontrast or single-phase imaging, useful for evaluating metastases beyond the liver 1, 2, 3

• MRI performance: Sensitivity of 90.8%-95.4% and specificity of 83.7%-89.8% for detecting malignant lesions 2

Lesions >1 cm in Chronic Liver Disease/Cirrhosis

• Preferred approach: Triple-phase contrast-enhanced CT (arterial, portal venous, delayed) or dynamic contrast-enhanced MRI interpreted with LI-RADS criteria 1, 2, 3

• Extracellular contrast agents preferred: For MRI-based HCC diagnosis, sensitivity is 71% and specificity 83% for 1-2 cm HCC with extracellular agents 2

• High-probability HCC: If AFP is elevated and the lesion is >2 cm in a cirrhotic liver, there is >95% probability of HCC; further imaging is primarily for treatment planning rather than diagnosis 2, 3

• CEUS in cirrhosis: For small nodules (1-2 cm), sensitivity, specificity, and accuracy for diagnosing HCC are 87%, 100%, and 93%, respectively 1

Lesions <1 cm

• In patients with known malignancy: MRI with and without IV contrast is the preferred modality 1, 3

• In chronic liver disease: Either MRI with and without IV contrast or multiphase contrast-enhanced CT is appropriate 1, 3

• Cirrhotic patients: Lesions <10 mm cannot be definitively diagnosed as HCC by imaging criteria and require surveillance 3

• Subcentimeter metastases: Between 78% and 84% of small hypodense lesions in patients with primary malignancy are benign 1

• CEUS for subcentimeter lesions: Correctly characterizes 95% of lesions overall and 98% of metastases in patients with indeterminate CT findings 1, 2, 3

Role of Percutaneous Biopsy

Biopsy should be reserved for lesions with inconclusive imaging or when histopathology is required for molecular testing; most benign lesions can be diagnosed definitively by imaging alone. 1, 2

• Indications: Only when imaging features indicate possible malignancy or when lesions such as lymphoma require histopathologic diagnosis 1, 2

• Avoid biopsy of benign lesions: Do not biopsy solid benign liver lesions such as hemangiomas or focal nodular hyperplasia; obtain diagnostic CT or MRI first 2

• CEUS-guided biopsy: Increases technical success rate from 74% to 100% for indeterminate lesions 2

• Biopsy risks: Post-biopsy bleeding risk is 9-12%, particularly with hypervascular lesions, and needle-tract seeding occurs in 0.1%-0.9% per year for HCC 2

• Subcentimeter lesions: Role of percutaneous biopsy is limited because such lesions are typically difficult to target under image guidance 1

Critical Pitfalls to Avoid

• Single-phase imaging inadequate: Single-phase CT or noncontrast imaging is insufficient for solid liver lesion characterization and should not be ordered 2

• LI-RADS misapplication: LI-RADS criteria must not be applied to patients without chronic liver disease or cirrhosis 2

• Obsolete modalities: Tc-99m sulfur colloid scans and Tc-99m RBC scans have no role in modern evaluation of indeterminate liver lesions 1, 3

• Ultrasound limitations: Ultrasound alone is insufficient for solid lesion characterization compared with cross-sectional imaging modalities 2

• Unenhanced CT/MRI: There is no added value for unenhanced images in routine liver lesion characterization 1

Special Considerations for Common Benign Lesions

• Simple hepatic cysts: Characterized by fluid attenuation on CT, strong T2 signal and low T1 signal on MRI, with no enhancement after contrast; require no treatment or follow-up once definitively characterized 4

• Hemangiomas: Display characteristic bright appearance on T2-weighted MRI and peripheral nodular enhancement with centripetal fill-in on dynamic imaging 1

• Focal nodular hyperplasia: Shows intense arterial phase enhancement, becomes isoattenuating in portal venous phase, and typically has a central scar with little enhancement in arterial phase 1