Hepatocellular Carcinoma

Published on 09/08/2015 by admin

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Last modified 09/08/2015

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 Small tumors (< 3 cm without vascular invasion) are curable with resection, ablation, transplantation

image Achievable goal of surveillance program using US, CT, &/or MR (properly performed and interpreted)
image Use LI-RADS classification system for focal lesions in cirrhotic liver
• Key imaging features

image Heterogeneous hypervascularity on arterial phase (CT or MR) with washout on venous and delayed
image Presence of a capsule or fat content
image Evidence of portal or hepatic vein invasion
image Hypointense lesion on hepatobiliary phase of gadoxetate-enhanced MR
image 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?

image Sonography

– Effective in expert hands in screening thin patients with relatively nonfibrotic livers
image 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
image
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

image Heterogeneous hypervascular mass with “washout” of contrast enhancement and portal vein invasion
• Size

image Small tumors < 2 cm
image Large tumors > 5 cm

– Diffuse: Subcentimeter to few cm lesions throughout liver
• Morphology

image Usually spherical
• Key concepts

image Most frequent primary visceral malignancy in world

– Accounts for 80-90% of all primary liver malignancies
image 2nd most common malignant liver tumor in children after hepatoblastoma
image 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
image 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

image 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

image Dominant hypodense mass with decreased attenuation “satellite” nodules
– Multifocal HCC: Multiple hypodense lesions rarely with central necrotic portion
image 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

image Hepatic arterial phase (HAP) scan

– Heterogeneous hypervascular enhancement (for moderately and poorly differentiated HCC)

image 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
image Portal venous phase (PVP) scan

– HCC often nearly isodense to surrounding liver
image Delayed scan: HCC hypodense to surrounding liver

– Washout of contrast enhancement is key finding

image Helps to distinguish HCC from regenerative nodules and arterioportal shunts (both common in cirrhosis)
image 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

image HCC may be hypo-, iso-, or hyperintense to liver
image Tumors with fat or hemorrhage are hyperintense
• T2WI

image Usually hyperintense to liver

– Regenerative nodules are hypointense on T2WI
image 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)

image Heterogeneously hyperintense, with washout on portal venous and delayed phase
image Rapid central washout with residual capsular enhancement = HCC, not arterioportal shunt
• Hepatobiliary contrast agent (gadoxetate)

image Trade names: Eovist or Primovist
image 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
image Increases sensitivity of MR in diagnosing small HCC
• Diffusion-weighted MR

image Restricted diffusion within HCC often detected as bright signal in focal lesion
image Adds sensitivity and specificity to MR detection of HCC

Ultrasonographic Findings

• Grayscale ultrasound

image Lower sensitivity and specificity than CT or MR in diagnosing HCC

– Especially within nodular, fibrotic, cirrhotic liver
image Mixed echogenicity due to tumor necrosis and hypervascularity
image Hypoechoic: Due to solid tumor
image Hyperechoic: Due to fatty metamorphosis

– Small hyperechoic HCC can simulate hemangioma
image Capsule: In encapsulated HCC

– Thin hypoechoic band
• Color Doppler

image Shows hypervascularity and tumor shunting
image Small HCC: Indistinguishable from regenerative and dysplastic nodules

Angiographic Findings

• Conventional

image Hypervascular tumor

– Marked neovascularity and AV shunting
– Large hepatic artery and vascular invasion
image Threads and streaks sign

– Sign of tumor thrombus in portal vein

Nuclear Medicine Findings

• Hepatobiliary scan

image Uptake in 50% of lesions
• Technetium sulfur colloid

image HCC in cirrhotic liver: Seen as defect
image HCC in noncirrhotic liver: Heterogeneous uptake
• Gallium scan

image HCC is gallium avid in 90% of cases

Imaging Recommendations

• Best imaging tool

image In cirrhotic patient, multiphasic CT or MR
image 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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