Liver and intrahepatic bile ducts - tumor
Benign tumors / conditions
Focal nodular hyperplasia (FNH)


Topic Completed: 6 March 2019

Revised: 30 May 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Focal nodular hyperplasia[TI] liver[TI] free full text[sb]

Omid Savari, M.D.
Joseph F. Tomashefski, Jr., M.D.
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Cite this page: Savari O, Tomashefski JF. Focal nodular hyperplasia (FNH). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/livertumorFNH.html. Accessed September 23rd, 2019.
Definition / general
Essential features
  • Solitary, well demarcated, unencapsulated, subcapsular hepatic nodule with central stellate scar on gross examination
  • Nodule with histologic features of biliary type cirrhosis with ductopenia in a background of noncirrhotic liver
  • Immunoreactivity for glutamine synthetase with a map-like pattern of staining
Terminology
  • Also known as focal cirrhosis, pedunculated adenoma, solitary hyperplastic nodule, mixed adenoma, hamartoma and hamartomatous cholangiohepatoma
ICD coding
Epidemiology
  • Most common in young adults, with rare reports of occurrence in childhood
  • More common in females than males (F:M = 8:1)
  • Accounts for ~8% of all primary liver tumors in adults (Dig Surg 2010;27:24)
  • Prevalence of 4 - 30 per 1,000 in adults and 0.2 per 1,000 in persons < 18 years (Dig Surg 2010;27:24)
Pathophysiology
  • Pathogenesis is not fully understood but is thought to occur as the result of a hyperplastic response to a vascular anomaly (Am J Surg Pathol 1999;23:1441)
  • Vascular endothelial growth factor is increased due to arterial hyperperfusion, which leads to activated hepatic stellate cells, which are responsible for fibrosis and characteristic central scar formation
Etiology
Diagrams / tables

Images hosted on other servers:

Possible pathogenesis

Clinical features
  • Usually asymptomatic
  • Lesion is often incidentally discovered during abdominal imaging or rarely as an abdominal mass identified during physical examination (HPB (Oxford) 2005;7:298)
Diagnosis
Laboratory
  • Abnormal liver function tests and gamma glutamyl transferase (GGT) have been reported in 12% of cases (Dig Surg 2010;27:24)
Radiology description
  • Well demarcated solitary hepatic lesion with a central scar in contrast CT scan and MRI
  • Angiography demonstrates "wheel spoke" appearance with the vessels radiating out from the center of the tumor (Clin Mol Hepatol 2016;22:199)
Radiology images

Images hosted on other servers:

Ultrasound and MRI

Prognostic factors
Case reports
Treatment
Gross description
  • Well demarcated but unencapsulated solitary lesion
  • Nodular appearance that is lighter in color than the surrounding liver parenchyma
  • Although usually a solitary nodule, it may be multifocal
  • Often located in the subcapsular region
  • Ranges in size from 1 to 10+ cm, although most nodules measure < 5 cm
  • Cut surface often shows a characteristic central scar with radiating fibrous septa, dividing the mass into smaller nodules
  • Rarely can present as a pedunculated mass (Proc (Bayl Univ Med Cent) 2018;31:97)
Gross images

Contributed by
Omid Savari, M.D.

Well circumscribed subcapsular mass


Contributed by
Hanni Gulwani, M.D.

Well
circumscribed
mass with central
stellate scar

Microscopic (histologic) description
  • Overall resembles a biliary type of cirrhosis with ductopenia in a background of noncirrhotic liver
  • Bland hepatocytes surrounded by fibrous septa that contain artery branches and variable degree of bile ductular reaction (most important distinguishing features) and variable amount of mixed inflammatory infiltrate
  • Portal tracts are absent except at the periphery of the lesion
  • Hepatocytes are usually similar to those in the surrounding liver
  • Hepatocyte plates are 1 - 2 cells thick and are supported by an intact reticulin framework
  • Mallory hyaline and other features of chronic cholestasis such as feathery degeneration and accumulation of excess copper may be found adjacent to the fibrous septa
  • Nuclear pleomorphism, prominent nucleoli and mitotic figures are absent in classical focal nodular hyperplasia (FNH) but cytologic atypia may be seen in variant forms
  • Medium to large sized, thick walled muscular vessels, often present in fibrous bands, which often exhibit myointimal myxoid or fibromuscular hyperplastic changes
  • In one study by Nguyen BN et al., different histologic variants are described (Am J Surg Pathol 1999;23:1441):
    • Classical
    • Nonclassical:
      • Telangiectatic: absence of a central scar and lack of architectural nodular distortion; hepatic plates are 1 cell thick and rather frequently appeared atrophic; plates are separated by sinusoid dilatation, sometimes alternating with areas of marked ectasia
      • Mixed hyperplastic and adenomatous form: presence of 2 alternating aspects, 1 resembling telangiectatic type FNH, the other simulating adenoma
      • FNH with cytologic atypia: atypical hepatocytes have an enlarged nucleus with an irregular nuclear contour, hyperchromasia, coarse granular chromatin and conspicuous nucleoli
      • FNH with steatohepatitis-like changes: may show overlapping features with steatohepatitic variant of hepatocellular carcinoma, such as widened cell plates or hepatocyte rosettes (Am J Surg Pathol 2017;41:277)
Microscopic (histologic) images

Contributed by Omid Savari, M.D.

Fibrous septae

Absent portal tracts

Nodular hepatocyte arrangement

Ductular reaction

Bland hepatocytes


Lack of atypia

Muscular vessels

Trichrome

Cytology description
  • In classical focal nodular hyperplasia (FNH), hepatocytes without significant atypia, arranged in trabeculae that are 2 cells thick
  • Bile ductular cells are helpful findings on cytology to differentiate FNH from hepatocellular adenoma (World J Surg Oncol 2004;2:5)
Positive stains
Molecular / cytogenetics description
  • mRNA expression alteration of the angiopoietin genes (ANGPT1 and ANGPT2) (Clin Mol Hepatol 2016;22:199)
  • Angiopoietin genes (ANGPT1 and ANGPT2) are involved in vascular maturation process
  • ANGPT1/ANGPT2 ratio increased compared with normal liver, cirrhosis and other liver tumors
  • Nonclonal β catenin activation, without mutations, has been shown to occur, contributing to hepatocellular hyperplasia and regeneration (Clin Mol Hepatol 2016;22:199)
Sample pathology report
  • Liver, right lobe lesion, needle core biopsy:
    • Liver parenchyma with features suggestive of focal nodular hyperplasia (see comment)
      • Comment: There is a history of an incidentally discovered right liver lesion. A well differentiated hepatocellular lesion with fibrous septa containing medium sized muscular arteries and inflammation is seen. Reticulin highlights normal hepatocyte cell plates. Glutamine synthetase demonstrates patchy staining of hepatocytes. CD34 shows patchy sinusoidal staining and beta catenin highlights normal membranous staining. Glypican 3 is negative. The morphology and immunoprofile are suggestive of focal nodular hyperplasia.
Differential diagnosis
  • Hepatocellular adenoma: no stellate scar, no ductular reaction, homogeneous parenchyma, perivascular and patchy glutamine synthetase expression
  • Fibrolamellar hepatocellular carcinoma: although grossly has similar features, microscopically, sheets of tumor cells with marked atypia and abundant eosinophilic cytoplasm are characteristic
  • Cirrhosis: diffuse changes in liver parenchyma
Board review question #1
Which immunohistochemistry stain is helpful to differentiate focal nodular hyperplasia from hepatocellular adenoma?

  1. Arginase
  2. HepPar1
  3. Glutamine synthetase
  4. Glypican 3
Board review answer #1
C. Glutamine synthetase with map-like staining can differentiate focal nodular hyperplasia from hepatocellular adenoma.

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Board review question #2
Which histologic feature helps to differentiate focal nodular hyperplasia from hepatocellular adenoma?

  1. Atypical hepatocytes
  2. Lack of portal tracts
  3. Portal tract chronic inflammation
  4. Presence of ductular reaction in fibrous bands
Board review answer #2
D. Presence of ductular reaction in fibrous bands is an important histologic feature that can help to distinguish focal nodular hyperplasia from hepatocellular adenoma.

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