Causes and Treatment of Focal Nodular Hyperplasia
What Is Focal Nodular Hyperplasia?
The liver is the only organ that is capable of self-regeneration, and this puts the organ at an inherent risk for developing atypical masses.
Focal nodular hyperplasia (FNH) is a solid, benign hepatic mass of non-vascular origin and this condition was described by Hugh Edmondson in 1958.
FNH is the second most common benign liver lesion.
FNH accounts for eight percent of all non-hemangiomatous liver lesions.
In most cases, FNH is asymptomatic lesions that require no treatment.
FNH is more common in females and is seen in young to middle-aged adults. The female to male ratio is 8:1.
FNH lesions can occur alone or in conjunction with other lesions like
Recent evidence point out that FNH can occur de nova after chemotherapy treatment like oxaliplatin.
Symptoms of FNH
Abdominal pain, Credits: pixabay
In most cases, FNH lesions are asymptomatic. Some patients may experience abdominal pain and gastrointestinal discomfort.
Types of FNH
FNH is divided into two
Typical FNH
Atypical FNH
Typical FNH
These types of lesions are characterized by a large appearance with well-circumscribed margins and poor encapsulation.
In less than 50% of cases, there is a prominent central scar with radiating fibrous septa. Histologically, the central scar consists of mature collagen surrounded by aberrant arteries, draining veins, and fibrous septae forming a pseudocapsule that distinguishes it from hepatocellular carcinoma, hepatocellular adenomas, and fibrolamellar hepatocellular carcinoma.
A large central artery is usually present with a spoke wheel like centrifugal flow. FNH lesions contain bile ductules and kupffer cells.
Atypical FNH
These types of lesions lack a central artery and a central scar. So they are difficult to distinguish from other types of lesions.
Atypical FNH lesions have pseudocapsule.
Causes of FNH
A Woman, Credits: pixabay
The exact cause of FNH remains unclear. It is caused by arterial malformations within the liver. These malformations, coupled with changes in perfusion, cause a regenerative, hyperplastic response of the normal hepatocyte.Any comorbid conditions that cause predisposition to the development of arterial malformations can increase the risk of FNH.
Osler-Weber-Rendu syndrome and the presence of hemangiomas can increase the risk of FNH.
There are also chances that a genetic mutation can be responsible for FNH, however, the mutation is yet to be identified.
As FNH is common in females, the condition can be linked to increased estrogen production. Females tend to have larger nodules than males.
Whether there is any association with the use of oral contraceptives and the risk of developing FNH is a matter of debate.
Treatment of FNH
Surgery, Credits: pixabay
If the lesions are asymptomatic a “wait and see approach” is followed. Ultrasound examinations are recommended every six months until a definite diagnosis is made.
If the disease is stabilized and there are no changes in the numbers and the size of nodules, the frequency of ultrasound examination can be reduced.
If there is evidence of progressive growth or large lesions and symptoms of compression or an increased risk of hemorrhage related to trauma, surgical resection is considered. Subcapsular nodules can be resected laparoscopically. In some instances, liver resection can be safely performed in specialized hepatobiliary centers.
Take-Home Message
FNH are benign liver lesions caused by arterial malformations within the liver.