In a 60‑year‑old asymptomatic woman with no known liver disease, ultrasound shows a 16 × 15 × 10 mm vascular, hypoechoic lesion in the right hepatic lobe with faint posterior acoustic shadowing that has enlarged from 13 × 14 × 8 mm, what are the most likely diagnoses and the recommended next‑step management?

Management of Enlarging Hypoechoic Hepatic Lesion in Asymptomatic 60-Year-Old Woman

This 16 mm lesion that has enlarged from 13 mm requires multiphasic contrast-enhanced CT or MRI as the next diagnostic step, because lesions between 1–2 cm with growth over time cannot be definitively characterized by ultrasound alone and need dynamic imaging to assess enhancement patterns that distinguish benign from malignant etiologies. 1

Differential Diagnosis

The most likely diagnoses for a vascular hypoechoic structure with faint posterior acoustic shadowing include:

• Hemangioma – Most common benign liver tumor; can appear hypoechoic in 27–30% of cases, particularly when smaller than 3 cm 2, 3. The faint posterior acoustic shadowing is atypical but can occur with mixed echogenicity patterns.

• Hepatocellular carcinoma (HCC) – Less likely in the absence of known cirrhosis or chronic liver disease, but the growth pattern (from 13 mm to 16 mm) raises concern and mandates exclusion 4, 1.

• Metastasis – Possible if there is occult primary malignancy, though less likely given the patient is asymptomatic. Metastases can present as hypoechoic lesions with variable acoustic properties 5.

• Focal nodular hyperplasia (FNH) – Typically hyperechoic or isoechoic, but can occasionally appear hypoechoic; usually shows characteristic spoke-wheel vascularity on Doppler 4.

• Hepatic adenoma – Rare, typically associated with oral contraceptive use; shows heterogeneous echogenicity and can have hemorrhagic components 4.

Critical Importance of Lesion Growth

The documented enlargement from 13 × 14 × 8 mm to 16 × 15 × 10 mm is the most concerning feature and fundamentally changes management. 4, 1

• Lesions <1 cm that remain stable over 1–2 years are very unlikely to be malignant and can return to routine surveillance 4, 1.

• However, any lesion that shows growth—even if it started below 1 cm—must be investigated using the algorithm for its current size 4.

• This lesion now measures 16 mm (1.6 cm), placing it in the 1–2 cm category where definitive characterization is both feasible and mandatory 4, 1.

Recommended Next-Step Management

Immediate Diagnostic Workup

Obtain multiphasic contrast-enhanced CT or MRI with arterial, portal venous, and delayed phases 4, 1:

• These modalities have 80–90% sensitivity for characterizing lesions in this size range 1.
• The enhancement pattern is diagnostic: arterial hyperenhancement with delayed washout suggests HCC, while peripheral nodular enhancement with centripetal fill-in suggests hemangioma 1.
• MRI may be slightly preferred over CT for lesions 1–2 cm due to superior soft tissue contrast 4.

Laboratory Testing

Check AFP (alpha-fetoprotein) level 4:

• AFP >200 ng/mL combined with characteristic imaging features allows HCC diagnosis without biopsy in cirrhotic patients 4, 6.
• However, AFP has poor sensitivity (39–65%) and should never be used alone to exclude malignancy 4.

Assess for underlying liver disease 1:

• Obtain liver function tests, hepatitis B and C serologies, and evaluate for metabolic liver disease risk factors.
• The presence or absence of cirrhosis fundamentally changes the differential diagnosis and diagnostic threshold 1, 6.

Size-Specific Algorithm for 1–2 cm Lesions

For lesions between 1–2 cm, guidelines recommend obtaining TWO dynamic imaging studies (CT, MRI, or contrast-enhanced ultrasound) 4:

• If both studies show typical HCC features (hypervascular in arterial phase with washout in portal/venous phase), treat as HCC without biopsy 4.
• If findings are not characteristic or vascular profiles are discordant between techniques, proceed to biopsy 4.

Role of Contrast-Enhanced Ultrasound (CEUS)

CEUS is an acceptable alternative to CT/MRI and can correctly characterize 89% of lesions, distinguishing benign from malignant in 97% of cases 2:

• Hemangiomas show peripheral nodular enhancement with centripetal fill-in 4.
• Malignant lesions typically show arterial hyperenhancement followed by washout 2.
• CEUS may be particularly useful for small hypervascular lesions where CT fails to demonstrate vascularity 2.

When to Consider Biopsy

Biopsy should be performed if 4, 6:

• The vascular profile on imaging is not characteristic or atypical.
• Two dynamic imaging studies show discordant findings.
• The lesion is detected in a non-cirrhotic liver and imaging is indeterminate.

Important caveats about biopsy 4:

• Needle track seeding risk ranges from 0–11%, with higher risk for subcapsular lesions 4.
• A negative biopsy cannot definitively exclude HCC, especially in small lesions where sampling error is common 4.
• Expert pathology interpretation is essential for distinguishing early HCC from dysplastic nodules 4.

Critical Pitfalls to Avoid

Do not continue ultrasound surveillance alone 1:

• Ultrasound cannot definitively characterize lesions in the 1–2 cm range, and documented growth mandates advanced imaging 4, 1.

Do not assume the lesion is benign based on "possibly cyst" description 1:

• The vascular nature and faint posterior shadowing are inconsistent with a simple cyst.
• Lesions denser than simple fluid require contrast-enhanced imaging 1.

Do not delay imaging if the patient has unrecognized cirrhosis or chronic liver disease 4, 1:

• In cirrhotic patients, lesions >1 cm have significant malignancy risk and require urgent evaluation 1, 6.
• Even in the absence of known liver disease, screen for occult cirrhosis given the HCC risk 1.

Do not biopsy if imaging shows classic hemangioma features 1:

• Characteristic peripheral nodular enhancement with centripetal fill-in on multiphasic imaging is diagnostic for hemangioma with 90–95% specificity 1.

Follow-Up Strategy if Initial Imaging is Indeterminate

If advanced imaging does not provide a definitive diagnosis 4, 6:

• Continue imaging surveillance every 3–6 months for up to 2 years 4.
• Consider repeat biopsy if the lesion enlarges further or develops characteristic features of malignancy 4.
• If no growth occurs over 1–2 years, the lesion is very unlikely to be HCC and routine surveillance can resume 4, 1.