Fibrolamellar hepatocellular carcinoma (FL-HCC) is a rare primary liver malignancy with distinct features that differentiate it from classic HCC. The vast majority of patients are young adults (ages 10-35) without underlying cirrhosis or chronic liver disease. AFP levels are typically normal — this is a critical laboratory finding for differentiation from classic HCC. The tumor is usually large at diagnosis (>10 cm) and contains a characteristic central calcified fibrous scar. Histologically, it is defined by lamellar fibrous bands interspersed between eosinophilic, oncocytic hepatocytes. The DNAJB1-PRKACA fusion gene is a pathognomonic genetic anomaly. Prognosis is relatively better than classic HCC; surgical resection is the primary treatment option with 5-year survival rates of 50-70% in resectable cases.
Age Range
10-35
Peak Age
25
Gender
Equal
Prevalence
Rare
The pathogenesis of FL-HCC is entirely different from classic HCC and does not arise in the setting of cirrhosis. At the molecular level, the DNAJB1-PRKACA fusion gene (~400 kb heterozygous deletion on chromosome 19p13.12) constitutively activates the protein kinase A (PKA) signaling pathway, leading to oncogenesis. The characteristic central fibrous scar results from fibrous tissue proliferation stimulated by neoplastic hepatocytes; this scar appears hypointense on T2-weighted images due to collagen accumulation and enhances in the delayed phase due to slow contrast uptake by fibrous tissue. The large tumor size reflects the slow but progressive growth pattern and late symptom onset. Calcification represents dystrophic calcification within the central scar and appears as a dense calcified focus on CT. Oncocytic hepatocytes contain abundant mitochondria; this mitochondrial richness increases cellular metabolic activity and explains heterogeneous arterial phase enhancement.
Central calcified fibrous scar in a large mass in non-cirrhotic liver of a young adult — distinguished from the non-calcified scar in FNH. This finding is highly specific for FL-HCC and when combined with T2 MR hypointense scar significantly increases diagnostic confidence.
Large (usually >10 cm), lobulated, heterogeneous density mass on non-contrast CT. Coarse calcification within the central fibrous scar — the most distinguishing CT finding for FL-HCC. Surrounding liver parenchyma is normal (no signs of cirrhosis).
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A _x_ cm lobulated, heterogeneous density mass is identified in liver segment _, containing a central scar with coarse calcification; the surrounding liver parenchyma is normal.
The mass demonstrates heterogeneous enhancement in arterial phase — solid components enhance prominently while the central scar does not enhance. The enhancement pattern is typically heterogeneous, unlike the homogeneous, intense arterial enhancement seen in FNH. Feeding hepatic artery branches may be enlarged.
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The mass demonstrates heterogeneous enhancement in the arterial phase with non-enhancing central scar.
In the delayed phase (3-5 minutes), the central fibrous scar shows progressive enhancement and becomes hyperintense relative to surrounding tumor tissue. This finding reflects the slow contrast uptake and late washout characteristic of fibrous tissue. The solid tumor components may show relative washout.
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In the delayed phase, the central scar shows progressive enhancement becoming hyperintense relative to the surrounding tumor.
On T1-weighted imaging, the mass is hypointense or isointense relative to liver parenchyma. The central fibrous scar is markedly hypointense on T1 (collagen deposition). T1 hyperintense areas within the tumor suggest hemorrhage or protein content. When hepatobiliary phase (gadoxetic acid) is used, FL-HCC shows hyposignal — due to loss of normal hepatocyte function.
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On T1-weighted sequence, the mass shows hypo/isointense signal relative to liver parenchyma with a markedly hypointense central scar.
On T2-weighted imaging, the mass is mildly to moderately hyperintense. Critical finding: the central fibrous scar is HYPOINTENSE on T2 — this is the most important MR criterion differentiating FL-HCC from FNH. The central scar in FNH is T2 hyperintense (contains edema and vessels), but the scar in FL-HCC is predominantly mature collagen and shows T2 hypointensity.
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On T2-weighted sequence, the mass shows mildly hyperintense signal with a markedly hypointense central scar; this finding is consistent with FL-HCC, distinct from the T2 hyperintense scar seen in FNH.
On diffusion-weighted imaging (DWI), the mass shows high signal with low values on ADC map. Diffusion restriction reflects the high cellularity of the tumor. The central fibrous scar shows relatively low signal on DWI (acellular fibrous tissue). ADC values are typically between 0.9-1.3 x 10⁻³ mm²/s.
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The mass demonstrates diffusion restriction on DWI with low values on the ADC map.
On B-mode ultrasonography, a large, heterogeneously echogenic mass is observed. The mass is usually well-defined with lobulated contour. The central scar may appear as a hyperechoic line or area; however, posterior acoustic shadowing is seen when calcification is present. Doppler ultrasonography demonstrates increased vascularity within the mass.
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A _x_ cm lobulated, heterogeneously echogenic mass is seen in liver segment _ with posterior acoustic shadowing at the central hyperechoic area.
On FDG PET-CT, the mass shows significant FDG uptake (SUVmax usually >5). The central scar is not metabolically active and appears as a photopenic area. PET-CT is used for staging — important for detecting lymph node and distant metastases.
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On FDG PET-CT, the liver mass demonstrates significant FDG uptake (SUVmax: _) with a photopenic central scar.
Criteria
Typical histological pattern: lamellar fibrous bands between large oncocytic hepatocytes. DNAJB1-PRKACA fusion gene positive. Usually solitary, large mass (>10 cm). Central calcified fibrous scar present.
Distinct Features
On imaging: heterogeneous arterial enhancement, T2 hypointense scar, delayed scar enhancement, normal AFP. Prognosis relatively good — 5-year survival 50-70% in resectable cases.
Criteria
FL-HCC variant without prominent central scar or with minimal fibrous component. Usually diagnosed at smaller size (<5 cm). Histologically FL-HCC pattern persists but macroscopic scar formation has not yet developed.
Distinct Features
Absence of calcified scar makes diagnosis more challenging — may be confused with other hypervascular tumors on imaging. Higher biopsy requirement.
Criteria
Tumor containing both fibrolamellar and classic HCC components. Areas of fibrolamellar and conventional hepatocellular carcinoma coexist. Presence or absence of cirrhosis is variable.
Distinct Features
Imaging features are variable depending on the relative proportion of both components. Prognosis is closer to classic HCC. Definitive diagnosis requires biopsy.
Criteria
FL-HCC presenting with lymph node metastasis and/or distant organ metastasis (lung, peritoneum). Lymph node involvement is more common in FL-HCC than in classic HCC (50-70% vs 5-10%).
Distinct Features
FDG PET-CT is very important for detecting lymph node and distant metastases at staging. Lymph node dissection during surgery is of critical importance.
Distinguishing Feature
In FNH the central scar is T2 hyperintense and does not contain calcification; in FL-HCC the scar is T2 hypointense and may be calcified. FNH shows homogeneous arterial enhancement while FL-HCC is heterogeneous. FNH is usually <5 cm; FL-HCC is usually >10 cm. FNH is iso/hyperintense on hepatobiliary phase; FL-HCC is hypointense.
Distinguishing Feature
Classic HCC develops in cirrhotic background in 85-90%; FL-HCC occurs in non-cirrhotic liver. AFP is usually elevated in HCC; normal in FL-HCC. Capsule and washout are expected in HCC (LI-RADS criteria); central calcified scar is expected in FL-HCC. HCC occurs in middle-older age (>50); FL-HCC in young adults (10-35 years).
Distinguishing Feature
Delayed enhancement is common in ICC but central calcification is rare; FL-HCC has an organized central calcified scar. ICC typically occurs in older age and is associated with biliary dilatation. Peripheral rim enhancement + central hypodensity is typical in ICC; heterogeneous arterial enhancement + central scar pattern is dominant in FL-HCC.
Distinguishing Feature
Hepatic adenoma is usually associated with oral contraceptive use in young women; FL-HCC has equal gender distribution. Adenoma shows homogeneous arterial enhancement and may contain fat/hemorrhage; the central calcified scar is distinguishing in FL-HCC. Calcification is not expected in adenoma.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
3-monthThe primary treatment for FL-HCC is surgical resection with aggressive surgical approach (extended hepatectomy + lymph node dissection). Since lymph node metastasis is frequent (50-70%), portacaval and hepatoduodenal ligament lymph node dissection should be performed. Liver transplantation may be considered in unresectable cases. Response to chemotherapy and radiation is limited. Five-year survival is 50-70% in resectable cases; below 20% in unresectable cases.
Fibrolamellar HCC has a better prognosis compared to conventional HCC. Surgical resection is the primary treatment with high resectability rates. Lymph node metastasis is more common than in conventional HCC. Transplantation may be considered in selected cases.