Small tumors (< 3 cm without vascular invasion) are curable with resection, ablation, transplantation
Achievable goal of surveillance program using US, CT, &/or MR (properly performed and interpreted)
Use LI-RADS classification system for focal lesions in cirrhotic liver
• Key imaging features
Heterogeneous hypervascularity on arterial phase (CT or MR) with washout on venous and delayed
Presence of a capsule or fat content
Evidence of portal or hepatic vein invasion
Hypointense lesion on hepatobiliary phase of gadoxetate-enhanced MR
Bright lesion on diffusion-weighted MR
TOP DIFFERENTIAL DIAGNOSES
• Regenerative and dysplastic nodules
• Cholangiocarcinoma (peripheral)
• Nodular regenerative hyperplasia
• Hypervascular metastases
CLINICAL ISSUES
• Which imaging modality should be used?
Sonography
– Effective in expert hands in screening thin patients with relatively nonfibrotic livers
Triphasic CT or MR (arterial, venous, and delayed phases) is mandatory in more advanced disease
– Any focal lesion; fibrotic, nodular liver; strong clinical concern for HCC
– MR with gadoxetate enhancement has greater sensitivity and specificity for analyzing nodules
The Liver Imaging Reporting and Data System (LI-RADS) is endorsed by the ACR for categorization of focal nodular lesions found on CT or MR in the cirrhotic liver. It is designed to standardize the interpreting and reporting of findings so that these are more uniform, accurate, and useful to referring physicians.
TERMINOLOGY
Abbreviations
• Hepatocellular carcinoma (HCC)
Synonyms
• Hepatoma
• Primary liver cancer
Definitions
• Most common primary malignant liver tumor, usually arising in a cirrhotic liver
IMAGING
General Features
• Best diagnostic clue
Heterogeneous hypervascular mass with “washout” of contrast enhancement and portal vein invasion
• Size
Small tumors < 2 cm
Large tumors > 5 cm
– Diffuse: Subcentimeter to few cm lesions throughout liver
• Morphology
Usually spherical
• Key concepts
Most frequent primary visceral malignancy in world
– Accounts for 80-90% of all primary liver malignancies
2nd most common malignant liver tumor in children after hepatoblastoma
Important to detect and stage accurately
– Small tumors are curable with resection, ablation, or transplantation
– Multiple, large, or those with venous invasion can be palliated with chemoembolization
Signs of portal vein invasion by HCC
– Expansion of portal vein lumen
– Enhancement of tumor within vein
– Contiguity of tumor and portal vein
CT Findings
• NECT
In noncirrhotic liver (usually a symptomatic patient, as with pain or rupture)
– Solitary HCC: Large hypodense mass; ± necrosis, fat, calcification
– Encapsulated HCC: Well-defined, rounded, hypodense mass
Dominant hypodense mass with decreased attenuation “satellite” nodules
– Multifocal HCC: Multiple hypodense lesions rarely with central necrotic portion
In cirrhotic liver (usually detected as part of a surveillance program)
– HCC may be hypodense to liver
– Regenerative nodules may be hyperdense to liver
• CECT
Hepatic arterial phase (HAP) scan
– Heterogeneous hypervascular enhancement (for moderately and poorly differentiated HCC)
Well-differentiated tumor may be hypodense to liver on all phases of enhancement
– Wedge-shaped areas of ↑ density on HAP: Perfusion abnormality due to portal vein occlusion by tumor thrombus and ↑ arterial flow
Portal venous phase (PVP) scan
– HCC often nearly isodense to surrounding liver
Delayed scan: HCC hypodense to surrounding liver
– Washout of contrast enhancement is key finding
Helps to distinguish HCC from regenerative nodules and arterioportal shunts (both common in cirrhosis)
Small hypervascular HCC
– Early and late arterial phases: Hyperattenuating, more on 2nd or later arterial phase
– Later (portal venous and delayed): HCC washes out to become hypodense to liver
MR Findings
• Variable intensity depending on degree of fatty change, fibrosis, necrosis
• T1WI
HCC may be hypo-, iso-, or hyperintense to liver
Tumors with fat or hemorrhage are hyperintense
• T2WI
Usually hyperintense to liver
– Regenerative nodules are hypointense on T2WI
HCC arising within dysplastic nodule
– “Nodule within nodule” pattern
– HCC appears as small focus of increased signal intensity within decreased signal intensity nodule
• T1 C+ (gadolinium)
Heterogeneously hyperintense, with washout on portal venous and delayed phase
Rapid central washout with residual capsular enhancement = HCC, not arterioportal shunt
• Hepatobiliary contrast agent (gadoxetate)
Trade names: Eovist or Primovist
On 20 minute delayed phase
– Normal liver (and some portions of cirrhotic liver) enhance brightly
– Most HCCs are seen as hypointense focal masses
– Rare for well-differentiated HCC to show delayed persistent enhancement with gadoxetate
Increases sensitivity of MR in diagnosing small HCC
• Diffusion-weighted MR
Restricted diffusion within HCC often detected as bright signal in focal lesion
Adds sensitivity and specificity to MR detection of HCC
Ultrasonographic Findings
• Grayscale ultrasound
Lower sensitivity and specificity than CT or MR in diagnosing HCC
– Especially within nodular, fibrotic, cirrhotic liver
Mixed echogenicity due to tumor necrosis and hypervascularity
Hypoechoic: Due to solid tumor
Hyperechoic: Due to fatty metamorphosis
– Small hyperechoic HCC can simulate hemangioma
Capsule: In encapsulated HCC
– Thin hypoechoic band
• Color Doppler
Shows hypervascularity and tumor shunting
Small HCC: Indistinguishable from regenerative and dysplastic nodules
Angiographic Findings
• Conventional
Hypervascular tumor
– Marked neovascularity and AV shunting
– Large hepatic artery and vascular invasion
Threads and streaks sign
– Sign of tumor thrombus in portal vein
Nuclear Medicine Findings
• Hepatobiliary scan
Uptake in 50% of lesions
• Technetium sulfur colloid
HCC in cirrhotic liver: Seen as defect
HCC in noncirrhotic liver: Heterogeneous uptake
• Gallium scan
HCC is gallium avid in 90% of cases
Imaging Recommendations
• Best imaging tool
In cirrhotic patient, multiphasic CT or MR
Triphasic CT or MR (arterial, venous, and delayed phases)
– MR with gadoxetate enhancement has greater sensitivity and specificity
DIFFERENTIAL DIAGNOSIS
Regenerative and Dysplastic Nodules
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