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Encyclopedia (browse by topic or system) Add Ar�clePa�ent Cases (browse by topic or system) Add Case Quiz Mode (diagnose from case presenta�ons)This site is targeted at medical and radiology professionals, contains user contributed content andmaterial that may be confusing to a lay audience. Use of this site implies acceptance of our Terms ofUse.

Focal nodular hyperplasia

Dr Henry Knipe ◉ and A.Prof Frank Gaillard ◉ et al.

Focal nodular hyperplasia (FNH) is a benign tumour-like mass of the liver, second only to cavernoushaemangiomas in frequency. It has characteris�c radiographic features in mul�-modality imaging butsome lesions may be atypical in appearance. FNH are usually treated conserva�vely.

Epidemiology

FNH is most frequently found in young to middle aged adults, with a strong female predilec�on 3-4;

~15% (range 10-20%) occur in men 7. Although exogenous oestrogens does not cause FNH, they have

been shown to increase the size of these masses 4. Solitary occurrence is more common.

Clinical presenta�on

These masses are either found incidentally on imaging or present due to mass effect with right upper

quadrant pain in 20% 5. Unlike hepa�c adenomas, FNH are only rarely complicated by spontaneous

rupture and haemorrhage 1,4.

Associa�ons

Associa�on with other benign lesions is commonly seen (~25%) 8:

hepa�c haemangiomas (most common) 6

hereditary haemorrhagic telangiectasiaarteriovenous malforma�ons (AVM)anomalous venous drainage

hepa�c adenoma (possible but not proven) 16

congenital absence of portal vein/portal vein atresiaBudd-Chiari syndromeportal shuntsidiopathic portal hypertension

portal or pulmonary hypertension 7

Pathology

The origin of FNH is thought to be due to hyperplas�c growth of normal hepatocytes with a malformedbiliary draining system. It is also thought to be in response to a pre-existent arteriovenous

malforma�on 1,4. The arterial supply is derived from the hepa�c artery whereas the venous drainage is

into the hepa�c veins. FNH does not contain portal venous supply 9.

FNH is divided into two types 4:

1. typical: 80%2. atypical: 20%

Typical FNH

Macroscopically, typical lesions demonstrate a tumour which is o�en quite large with wellcircumscribed margins but poorly encapsulated. A prominent central scar is usually noted with

radia�ng fibrous septae: <50% of cases 7. A large central artery is usually present with spoke-wheel like

centrifugal flow 3-4 (no portal veins).

Histologically the lesion is mul�nodular, composed of nearly normal hepatocytes arranged in 1-2 cell

thick plates. Bile ductules are usually found at the interface between hepatocytes and fibrous regions 1-

2. Kupffer cells are present 4,7.

There is essen�ally no malignant poten�al 1.

Atypical FNH

An atypical FNH essen�ally refers to a lesion which lacks the central scar and central artery, and is thus

harder to dis�nguish from other lesions on gross inspec�on and imaging 4.

Atypical features also include pseudocapsule, lesion heterogeneity (more commonly seen in adenoma),

non enhancement of the central scar and intralesional fat 6.

Nodules can grow and disappear and new nodules can appear even a�er resec�on 7.

Variants

Some authors also describe division of atypical FNH into several variants which include 8:

telangiecta�c variantmixed hyperplas�c and adenomatous variantlesions with large cell hepatocellular atypia

Radiographic features

As FNH is usually treated conserva�vely, accurate imaging is essen�al in preven�ng unnecessaryinterven�on.

It should be noted that up to 20% of pa�ents with an FNH will have mul�ple lesions 4 and a further 23%

will have haemangiomas 4.

Ultrasound

The echogenicity of both FNH (and its scar) is variable and it may be difficult to detect onultrasound. Some lesions are well marginated and easily seen whereas other are isoechoic withsurrounding liver. Detectable lesions characteris�cally will demonstrate a central scar with displacementof peripheral vasculature on colour Doppler examina�on, however these findings are seen in only 20%

of cases 4.

contrast-enhanced ultrasound 14:arterial phase

FNH will enhance rela�ve to background liverprominent feeding vessel may be seen

portal venous phasecentrifugal filling (opposite to haemangioma and adenoma)sustained enhancement in the portal venous phaseunenhanced scar may be present

CT

A mul�-phase scan is ideal, commonly comprising 4:

non-contrastarterial (25-35 second delay)portal venous (60-70 second delay)delayed (5-10 minute delay)

On the non contrast series, the lesion is usually hypo- or isoa�enua�ng, but may appearhypera�enua�ng if the rest of the liver is fa�y. A hypoa�enua�ng central scar can be seen in up to 60%

of lesions >3 cm in size 4.

FNH demonstrates bright arterial contrast enhancement except for the central scar which remains

hypoa�enua�ng 4. Enlarged central arteries may be seen.

In the portal venous phase the lesion becomes isoa�enua�ng to liver.

The scar demonstrates enhancement on delayed scans in up to 80% of cases 4

MRI

Liver MRI is both sensi�ve (70%) and specific (98%).

Signal characteris�cs

T1iso to moderately hypointensehypointense central scar

T2iso to somewhat hyperintensehyperintense central scar

contrast studiesT1 C+ (Gd)

intense early arterial phase enhancement, similar to CT

central scar retains contrast on delayed scans 13

isointense to liver on portal venous phase 10-12

T1 C+ (Eovist) early arterial enhancement

enhancement persists into delayed phases 11

fades toward background liver intensity on the delayed hepatobiliary phase, with asmall amount of enhancement remaining (c.f. adenomas which classically arehypointense rela�ve to liver on hepatobiliary phase)

T2* C+ (re�culoendothelial agent: SPIO) hypointense mass as a result of suscep�bility signal loss due to uptake by Kupffer cells

Nuclear medicine

The presence of Kupffer cells in FNH allows these lesions to take up techne�um (Tc) 99m sulphurcolloid. P\A posi�ve scans is seen in 80% of lesions, and is helpful in dis�nguishing them from hepa�c

adenomas, HCC and hepa�c metastases which, usually but not always, do not contain Kupffer cells 4.

Treatment and prognosis

FNH is benign, with no malignant poten�al and a very small risk of complica�on (rupture,

haemorrhage) and thus are usually treated conserva�vely 1.

Differen�al diagnosis

General imaging differen�al considera�ons include:

hepa�c adenomahepatocellular carcinoma (HCC)

fibrolamellar HCChypervascular hepa�c metastasis/metastaseshepa�c haemangioma

Prac�cal points

be wary of calling a hypervascular lesion in a cirrho�c liver an FNH, unless defini�vely able toprove it is not HCCFNH typically has no capsule; if a hypervascular liver mass has a capsule, put HCC above FNH onthe differen�althere is likely overlap in appearance between FNH and inflammatory hepa�c adenoma when usinggadoxe�c acid (Eovist); if the pa�ent has risk factors (e.g. metabolic syndrome), consider both on a

differen�al 15

Related ar�cles

Hepatobiliary pathology

deposi�onal disorders[+]infec�on and inflamma�on[+]malignancy

liver and intrahepa�c bile duct tumoursbenign epithelial tumours

hepatocellular hyperplasiahepa�c regenera�ve nodulefocal nodular hyperplasia

hepatocellular adenoma[+]hepa�c/biliary cysts[+]

benign nonepithelial tumours[+]primary malignant epithelial tumours[+]primary malignant nonepithelial tumours[+]hematopoeie�c and lymphoid tumours[+]secondary tumours[+]miscellaneous[+]

extrahepa�c bile duct tumoursmetabolic[+]trauma[+]vascular[+]

Ultrasound - liver

ultrasound (introduc�on)liver ultrasound

liverfocal

hyperechoic liver lesionshypoechoic halo sign / target lesionssimple hepa�c cysthepa�c haemangioma

focal nodular hyperplasiahepa�c adenomahepa�c metastases[+]hepa�c abscess

diffuse[+]hepa�c vasculature[+]other[+]

liver transplant[+]biliary[+]

References

Edit Ar�cle Share

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URL of Ar�clehttp://radiopaedia.org/articles/focal-nodular-hyperplasia

Ar�cle Informa�on:

rID: 6749System: HepatobiliarySec�on: PathologyTags: liver, eovistSynonyms or Alternate Spellings:

FNHFocal nodular hyperplasia (FNH)

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