Hepatocellular Carcinoma

Quick Answer

In hepatocellular carcinoma, nuclear medicine's principal role is therapeutic: Y-90 radioembolization (TARE/SIRT) delivers high tumor radiation dose through the hepatic artery — used across intermediate/advanced stages, for downstaging to transplant/resection, and as radiation segmentectomy for localized disease. A mandatory ⁹⁹ᵐTc-MAA mapping study precedes treatment to measure the lung-shunt fraction and detect extrahepatic deposition. Diagnostic FDG-PET is limited (well-differentiated HCC is often FDG-low), though FDG avidity carries adverse prognostic weight.

Definition

Hepatocellular carcinoma (HCC) is a primary malignancy of hepatocytes, arising in the large majority within chronic liver disease / cirrhosis. It is characteristically hypervascular (arterially supplied), a property exploited by both contrast-imaging diagnosis and transarterial therapy.

Synonyms

HCC; hepatoma (older term); primary liver-cell carcinoma. Related but distinct: cholangiocarcinoma (biliary), combined HCC-cholangiocarcinoma, and fibrolamellar HCC (young, non-cirrhotic).

Epidemiology

HCC is one of the most common causes of cancer death worldwide, with a strong male predominance. The dominant risk factors are chronic HBV and HCV, alcohol-related cirrhosis, and — increasingly — metabolic dysfunction-associated steatohepatitis (MASH/NASH); aflatoxin exposure contributes in some regions. Incidence tracks the underlying liver-disease epidemiology of each population.

Etiology & Risk Factors

• Cirrhosis of any cause (the dominant substrate).
• Chronic HBV (can cause HCC even without cirrhosis), HCV, alcohol, MASH, hereditary hemochromatosis, α1-antitrypsin deficiency.
• Aflatoxin B1 (synergistic with HBV).

Pathophysiology

Chronic injury drives a stepwise progression: regenerative nodule → dysplastic nodule → HCC, accompanied by arterialization (loss of normal portal supply, gain of abnormal hepatic-arterial neovascularity). This arterialization underlies the LI-RADS hallmark of arterial-phase hyperenhancement with washout and enables transarterial delivery of Y-90 microspheres directly to tumor. Portal-vein invasion and intrahepatic/extrahepatic spread mark advanced disease.

Genetics & Molecular Biology

Common somatic events include TERT promoter mutations (early), TP53, CTNNB1 (β-catenin), and axis alterations in cell-cycle and chromatin genes. Molecular class does not yet drive routine imaging, but well-differentiated tumors retain hepatocyte metabolic machinery — including glucose-6-phosphatase, which dephosphorylates FDG-6-phosphate and causes tracer washout (the reason well-differentiated HCC is FDG-low).

Histopathology

Graded from well- to poorly-differentiated. Well-differentiated HCC resembles hepatocytes (retains function, low GLUT/high G6Pase → FDG-poor); poorly-differentiated HCC loses this (FDG-avid, adverse). Immunostains (HepPar-1, arginase-1, glypican-3) confirm hepatocellular origin when biopsy is performed.

Clinical Presentation

Often asymptomatic and screen-detected in patients under cirrhosis surveillance. Symptomatic disease brings right-upper-quadrant pain, weight loss, hepatic decompensation (ascites, jaundice, variceal bleeding), or paraneoplastic phenomena (hypoglycemia, erythrocytosis, hypercalcemia). Portal-vein tumor thrombus may present with rapid decompensation.

Laboratory Findings

• Alpha-fetoprotein (AFP) — surveillance/diagnostic adjunct and prognostic marker (not specific/sensitive alone).
• Liver function and Child-Pugh / ALBI grade — central to therapy selection and prognosis.
• Viral serologies and iron studies for etiology.

Imaging Findings by Modality

• Multiphase CT / MRI (LI-RADS): the diagnostic reference — arterial hyperenhancement + washout + capsule/threshold growth can diagnose HCC without biopsy in an at-risk liver.
• Ultrasound (± AFP): surveillance in cirrhosis.
• ⁹⁹ᵐTc-MAA mapping (SPECT/CT): pre-Y-90 planning — lung-shunt fraction and extrahepatic deposition.
• FDG-PET: limited for diagnosis (well-differentiated HCC FDG-low); FDG avidity is prognostic (higher grade, worse outcome, extrahepatic-metastasis risk).
• Post-Y-90 imaging: Y-90 bremsstrahlung SPECT or Y-90 PET to confirm distribution.

Radiopharmaceutical Uptake Mechanisms

⁹⁹ᵐTc-MAA microspheres lodge in tumor arterioles, simulating microsphere distribution to quantify hepatopulmonary shunting and detect gastrointestinal deposition. FDG is trapped less in well-differentiated HCC because retained glucose-6-phosphatase dephosphorylates and clears it; C-11-acetate/choline (research) complements FDG in well-differentiated tumors. Therapeutic ⁹⁰Y microspheres deliver short-range β-radiation at the tumor's arterial supply.

Typical PET / Tracers

Therapy Indications (BCLC-Guided)

• Very early/early (BCLC 0/A): ablation, resection, or transplant (Milan criteria); radiation segmentectomy (ablative Y-90 to 1–2 segments) as a curative-intent option.
• Intermediate (BCLC B): TACE or Y-90 radioembolization; downstaging to transplant/resection.
• Advanced (BCLC C): systemic therapy — atezolizumab + bevacizumab (first-line), durvalumab + tremelimumab, lenvatinib, sorafenib; Y-90 in selected liver-dominant disease.
• Terminal (BCLC D): best supportive care.

Theranostics

HCC's dominant nuclear therapy is ⁹⁰Y radioembolization — a liver-directed, transarterial delivery of β-radiation with personalized dosimetry improving outcomes (DOSISPHERE-01) and radiation segmentectomy achieving high local control in early HCC (LEGACY). The ⁹⁹ᵐTc-MAA "simulation" before therapy is the planning/safety companion — a theranostic-style image-then-treat workflow (see the Y-90 therapy and lung-shunt pages).

Differential Diagnosis

• Dysplastic/regenerative nodules and arterialized pseudolesions in cirrhosis.
• Intrahepatic cholangiocarcinoma and combined HCC-CCA (different enhancement/behavior).
• Metastasis, hemangioma (RBC-scan fill-in), and focal nodular hyperplasia (sulfur-colloid uptake).

Reporting Checklist

• For diagnosis, apply LI-RADS in the at-risk liver (arterial hyperenhancement, washout, capsule).
• For Y-90 planning, report lung-shunt fraction and any extrahepatic (GI) deposition requiring coil embolization; note dosimetry approach.
• Post-therapy, confirm microsphere distribution (bremsstrahlung SPECT / Y-90 PET).
• Contextualize any FDG finding as prognostic (avidity = higher grade), not diagnostic.

Prognosis

Prognosis integrates tumor stage (BCLC), liver function (Child-Pugh/ALBI), and performance status. Portal-vein invasion and extrahepatic spread are adverse; FDG avidity predicts higher grade, extrahepatic disease, and worse survival. Curative options (transplant, resection, ablation, radiation segmentectomy) in early disease offer the best outcomes.

Board Pearls

In HCC, nuclear medicine's role is therapeutic, not diagnostic: Y-90 radioembolization (across intermediate/advanced disease, for downstaging, and as ablative radiation segmentectomy) after a mandatory ⁹⁹ᵐTc-MAA mapping study measuring the lung-shunt fraction (the gatekeeper limiting deliverable activity) and detecting extrahepatic GI deposition.

Well-differentiated HCC is often FDG-negative (retained glucose-6-phosphatase clears the tracer), so a negative FDG-PET does not exclude HCC — but FDG avidity marks higher grade and worse outcomes.

Personalized dosimetry improved response over standard dosimetry (DOSISPHERE-01), and radiation segmentectomy delivers ablative segmental doses for early HCC (LEGACY) — so Y-90 spans palliative-to-curative intent. Never proceed to Y-90 without accounting for a high lung-shunt fraction (radiation-pneumonitis risk) and extrahepatic deposition.

Related Pages

• Therapy: ⁹⁰Y radioembolization (SIRT); tool: lung-shunt fraction calculator.
• Related disease: Colorectal & esophagogastric cancer (liver-dominant metastases also treated with Y-90).
• Tracer: ⁹⁹ᵐTc-MAA and FDG.

Figure / Diagram Suggestions

• A BCLC-to-therapy map highlighting where Y-90 (segmentectomy, intermediate, downstaging) fits.
• The MAA simulation → Y-90 delivery workflow with lung-shunt gating.
• Well- vs poorly-differentiated HCC FDG behavior (G6Pase washout vs avid).

Common Pitfalls

• Free ⁹⁹ᵐTc-pertechnetate from poorly-labeled MAA falsely elevates the lung-shunt fraction and adds gastric/thyroid activity that can be mistaken for extrahepatic GI deposition — check label quality before acting on shunt numbers.
• Assuming the MAA "simulation" perfectly predicts Y-90 microsphere distribution: catheter repositioning, differing particle load, and altered arterial flow between mapping and treatment can produce a mismatch.
• Judging treated-lesion response by size: after Y-90/TACE a lesion may transiently enlarge or not shrink; viability is assessed by arterial enhancement (mRECIST), not diameter.
• Treating a negative FDG-PET as reassurance: well-differentiated HCC is characteristically FDG-low, so FDG cannot exclude or "clear" viable tumor — it only stratifies grade/prognosis when positive.

Self-Check (Board-Style)