Ultrasound examination (ultrasound)
Outside the US, ultrasound is widely used for screening. The rule of thumb is: any new solid lesion in a high-risk patient should be considered a potential carcinoma.
The echogenicity of small nodules can be either increased or decreased relative to the normal liver parenchyma.
- Capsule: sometimes visualized as an outer hypoechoic rim.
- Structure: large nodules are heterogeneous due to hemorrhage, necrosis, or fat accumulation. A specific "nodule-in-a-nodule" (nodule in a nodule) appearance can be observed.
- Doppler ultrasound: high-velocity signals within the lesion are recorded, resulting from arterioportal shunting.
Computed tomography (CT)
Multiphasic CT is mandatory. On unenhanced (non-contrast) scans, the tumor appears as a low-density area with indistinct margins. Internal calcifications are rare (seen in 7.5% of cases).
Enhancement patterns:
- Late arterial phase: most HCCs are hypervascular and show avid contrast enhancement. This phase is critically important as many lesions are visible only during it.
- Portal venous and delayed phases: characterized by contrast "washout" (washout), during which the nodule becomes hypoattenuating relative to the surrounding tissue.
- "Mosaic" pattern (*mosaic):* a reticular enhancement pattern (grid-like pattern) is sometimes observed, followed by delayed peripheral enhancement.
Magnetic resonance imaging (MRI)
MRI is the most sensitive diagnostic modality. Classic semiotics include:
- T1-weighted images (T1WI): decreased (hypointense) signal. Occasionally, the signal is increased due to fat or glycogen accumulation.
- T2-weighted images (T2WI): moderately increased signal with internal heterogeneity.
- Contrast enhancement: the classic triad persists — avid enhancement in the late arterial phase and washout in the portal venous or delayed phases (at 5–10 minutes).
An atypical appearance occurs in 5–10% of cases: avascular lesions, high signal on T1WI, or low signal on T2WI. The presence of fat within the tumor can be confirmed using gradient-echo sequences: on out-of-phase series (out-of-phase), the signal from lipids drops.
Differential diagnosis and tumor thrombosis
It is important to differentiate HCC from regenerative and dysplastic nodules in cirrhosis. Such nodules may actively enhance in the arterial phase but do not show typical "washout". Furthermore, they are often hyperintense on T1WI and hypointense on T2WI due to iron accumulation.
A frequent complication of HCC is invasion into the branches of the portal vein. Unlike a bland thrombus, a malignant tumor thrombus (tumour thrombus):
- Has an expansile nature (expands the vessel lumen).
- Avidly enhances in the arterial phase (like the primary tumor).
- Demonstrates "washout" in the equilibrium phase.
Briefly: answers to topical questions
What complications are characteristic of hepatocellular carcinoma?
Hepatocellular carcinoma is characterized by vascular complications and spontaneous tumor rupture.
- Portal vein thrombosis is a frequent complication accompanied by the formation of a tumor thrombus (tumour thrombus), which can expand the vessel lumen.
- Spontaneous rupture is a disruption of the tumor capsule integrity, which may manifest clinically as an "acute abdomen" syndrome.
What are the macroscopic growth patterns of hepatocellular carcinoma?
Three macroscopic growth forms of hepatocellular carcinoma are distinguished:
- nodular;
- massive;
- diffuse-infiltrative.
Grossly, the tumor may present as a single nodule or multiple nodules. The color is pale brown or green, as HCC cells can produce bile. Liver weight can increase up to 2000–3000 g.
What system is used to stage hepatocellular carcinoma for treatment planning?
To determine the treatment strategy for hepatocellular carcinoma, the Barcelona Clinic Liver Cancer (Barcelona Clinic Liver Cancer — BCLC) staging system is used. It provides a treatment algorithm tailored to the specific stage, taking into account the extent of the tumor process, liver functional status according to Child-Pugh, and the patient's performance status. There are 5 stages of the disease:
- 0 — very early stage.
- A — early stage.
- B — intermediate stage.
- C — advanced stage.
- D — terminal stage.
What hepatospecific contrast agents are used in MRI diagnosis of hepatocellular carcinoma?
In the MRI diagnosis of hepatocellular carcinoma, a hepatospecific contrast agent, gadoxetic acid (gadoxetic acid), is used. Its administration allows for a hepatospecific (hepatobiliary) phase of the study. Against the background of the contrast-enhanced healthy liver parenchyma, hepatocellular carcinoma demonstrates a typical diagnostic sign — low signal intensity. The use of this drug is especially recommended for detecting early cancer up to 2.0 cm in size in patients with liver cirrhosis or chronic viral hepatitis B.
Classic HCC contrast triad: "In — Out — Capsule remains". Contrast actively enters in the arterial phase (hypervascularity), rapidly washes out in the portal phase (washout), and the capsule is visualized in the delayed phase.
Class and exam questions
How does a dysplastic nodule differ from HCC on contrast enhancement?
Atypical dysplastic nodules may enhance in the arterial phase, however, unlike carcinoma, they do not demonstrate the characteristic washout phenomenon in delayed phases.
How to reliably identify a tumor thrombus on MRI?
Standard T2WI sequences are unreliable. Dynamic contrast-enhanced imaging must be used: a malignant thrombus will expand the vessel, enhance in the arterial phase, and demonstrate washout.
Can treatment efficacy be assessed in the first month following therapy?
Ultrasound, CT, and contrast-enhanced MRI are considered unreliable in the first 4–6 weeks. However, diffusion-weighted imaging (DWI) with ADC map evaluation is successfully used early on: ADC values increase in areas of necrosis.
What else to study on this topic
- Limitations of hepatotropic contrast agents in well-differentiated HCC
- Fibrolamellar carcinoma (FLC) and the diagnostic significance of the central calcified scar
- Diffusion-weighted imaging (DWI) and ADC maps for detecting small lesions
- Differential diagnosis of HCC with epithelioid hemangioendothelioma
- Impact of hepatic steatosis on metastasis detectability on unenhanced CT
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