Focal nodular hyperplasia

Focal nodular hyperplasia (FNH) is a benign tumor of the liver (hepatic tumor), which is the second most prevalent tumor of the liver (the first is hepatic hemangioma). It is usually asymptomatic, rarely grows or bleeds, and has no malignant potential. This tumour was once often resected because it was difficult to distinguish from hepatic adenoma, but with modern multiphase imaging is usually now diagnosed by strict imaging criteria and not resected.

Focal nodular hyperplasia
Micrograph of focal nodular hyperplasia. H&E stain.
SpecialtyGastroenterology 

Presentation
Ultrasound of malformed vessels within the fibrous scar of FNH.
Liver tumor types by relative incidence in adults in the United States, with focal nodular hyperplasia at right.[1]

Focal nodular hyperplasia's most recognizable gross feature is a central stellate scar seen in 60–70% of cases. Microscopically, a lobular proliferation of bland-appearing hepatocytes with a bile ductular proliferation and malformed vessels within the fibrous scar is the most common pattern. Other patterns include telangiectatic, hyperplastic-adenomatous, and lesions with focal large-cell dysplasia.[2] Rarely, these lesions may be multiple or can occur as part of a syndrome with hemangiomas, epithelioid hemangioendothelioma, hepatic adenomas, fibrolamellar hepatocellular carcinoma, vascular malformations of the brain, meningiomas, and/or astrocytomas.[2]

Pathophysiology

FNH is not a true neoplasm; it is believed to result from localized hyperplastic hepatocyte response to an underlying congenital arteriovenous malformation. It consists of normal liver constituents in an abnormally organized pattern, grows in a stellate pattern and may display central necrosis when large.[3] Additionally evidence suggests that the incidence of FNH is related to oral contraceptive use.[4]

Diagnosis

Triple phase CT scan, or MRI are generally diagnostic. If still unable to differentiate from a hepatic adenoma, a sulfur colloid scan may be obtained. This will be positive in FNH, but not in an adenoma due to less Kupffer cells being present to uptake the colloid.

Notes
  1. Table 37.2 in: Sternberg, Stephen (2012). Sternberg's diagnostic surgical pathology. Place of publication not identified: LWW. ISBN 978-1-4511-5289-0. OCLC 953861627.CS1 maint: ref=harv (link)
  2. Nguyen, Bich N.; Fléjou, Jean-François; Terris, Benoit; Belghiti, Jacques; Degott, Claude (1999). "Focal Nodular Hyperplasia of the Liver". The American Journal of Surgical Pathology. 23 (12): 1441–54. doi:10.1097/00000478-199912000-00001. PMID 10584697.
  3. Imaging in Focal Nodular Hyperplasia at eMedicine
  4. Scalori, Astrid; Tavani, Alessandra; Gallus, Silvano; La Vecchia, Carlo; Colombo, Massimo (2002). "Oral contraceptives and the risk of focal nodular hyperplasia of the liver: A case-control study". American Journal of Obstetrics and Gynecology. 186 (2): 195–7. doi:10.1067/mob.2002.120277. PMID 11854634.
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References
Classification
External resources
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