Focal nodular hyperplasia: Description, Causes and Risk Factors:
Focal nodular hyperplasia of the liver is a rare liver cell-derived benign tumor. It is well described in its classical form, characterized by a stellate central scar and hyperplastic nodules since it was first introduced by Edmondson in 1958. Most FNH are asymptomatic and are discovered incidentally during physical examination, abdominal surgery, or autopsy, but some large FNH may be associated with significant symptoms.
To this day, the nature and pathogenesis of FNH remain controversial, but two predominant theories exist. FNH may be a response to a preexisting vascular abnormality. The artery associated with the central scar is larger than normal and causes hyperperfusion in this region and/or arterialization of sinusoids, with resulting hyperplasia of the surrounding parenchyma. Growth of surrounding hepatocytes stops when the sinusoids are compressed and vascular resistance increases with slowing of the blood ?ow. The second theory relates to the use of oral contraceptives. In contrast to adenoma, the origin of FNH has not been de?nitively linked to estrogen, but based on isolated reports, it is still thought that estrogen may act as a growth factor and can increase the size and vascularity of the nodules. Therefore, in any patient with FNH, the use of oral contraceptives should be strongly discouraged.
Another important ?nding among patients with multiple FNH is an identi?ed association with other vascular malformations and/or neoplasia. The most frequent associations include arterial dysplasia, portal vein atresia, berry aneurysm of the brain, and pulmonary arterial hypertension. There are additional associations with meningioma, astrocytoma, liver hemangioma, and Klippel-Trenaunay and von Recklinghausen syndromes.
Genetic abnormalities and inherited conditions - Focal nodular hyperplasia is also seen to occur in people with inherited conditions such as hemorrhagic telangiectasia. This is an inherited condition characterized by vascular malformations as well. This genetic predisposition causes vascular malformation in the liver and eventually leads to focal nodular hyperplasia.
- Past childhood malignancy - If a child had been treated for a past malignancy, he/she is at a higher risk of developing focal nodular hyperplasia. This is observed in clinical studies where 138 patients who received treatment for malignancies developed focal nodular hyperplasia. The incidence rate is at 045% of the cases.
Focal nodular hyperplasia tends to affect women much more frequently than men, though doctors are unsure why that is the case. Most patients diagnosed with the condition are over the age of 30. Tumors do not affect liver functioning or cause physical symptoms in the vast majority of cases. Rarely, a tumor can grow large enough to put pressure on the liver and surrounding organs, leading to abdominal pain. A chemical that is found in oral contraceptives can trigger a hemorrhage in the tumor, though excessive bleeding is very rare.
In most patients, the clinical course is silent, and FNH is incidentally discovered during cross-sectional imaging, angiography, radionuclide liver scanning, or surgery. In most cases, FNH occurs as a solitary lesion (80-95%), but multiple lesions may occur. Although FNH usually has no clinical significance, recognition of the radiologic characteristics of FNH is important to avoid unnecessary surgery, biopsy, and follow-up imaging.
Malignant transformation of FNH has not been reported. FNH must be differentiated from a fibrolamellar variant of hepatocellular carcinoma, with which it shares imaging and gross features.
Only a third of the cases of focal nodular hyperplasia show symptoms. These cases may indicate an increased rate of cellular proliferation that is enough to cause signs and symptoms.When focal nodular hyperplasia is suspected or seen, it manifests the following clinical presentation:
Gross feature is a scar with a stellate center, when the tumor is dissected and examined; a star-like scar is seen at the center of the growth.
- Large numbers of bland appearing hepatocytes proliferate the lobules of the liver and this is accompanied by the presence of bile compound and malformed blood vessels.
- Telangiectasia is also seen, this is a condition where small blood vessels become dilated. This is often accompanied by cellular changes such as dysplasia.
- Slower rate biliary secretion.
- Tumors may be present on the liver surface or pedunculated.
- Most lesions are smaller than 5cm most with an average diameter of 3 cm.
- In some cases the lesion replace a lobe of the liver, this is then called lobar focal nodular hyperplasia.
It is common for focal nodular hyperplasia to go unnoticed until the growth is seen in diagnostic imaging tests for other conditions. A doctor who is screening for cancer, internal injuries, or other disorders near the abdomen may notice the abnormal mass of hepatocytes. Once focal nodular hyperplasia is discovered, doctors commonly perform additional screening tests and take a biopsy of tissue to make sure that the tumor is not malignant.
Preoperative diagnosis of FNH mainly depends on imaging examination such as color Doppler flow imaging (CDFI), computed tomography (CT) and magnetic resonance imaging (MRI), but they all have limitations. By combining various imaging techniques, the rate of definite diagnosis is generally 50% and sometimes over 80%. It is difficult to make a definite preoperative diagnosis for FNH and to differentiate FNH from other benign and malignant tumors before operation, especially when the focus is small.
Nonoperative therapy is the standard treatment because FNH is a benign process and the majority of patients are asymptomatic. But invasive therapy, including transarterial embolization and resection, are recommended for those patients with clinical symptoms or indefinite diagnosis.
This condition is rare and for most treatment nor surgery is not indicated. However on certain instances, a liver resection may be indicated. Surgery involves liver resection. Liver resection is the removal of a part of the liver that is diseased or affected. In focal nodular hyperplasia, the part of the liver where there is tumor growth is removed. The healthy part of the liver is left unharmed. A person can still continue normal functioning despite the removal of one part of the liver.
Moderation in alcohol, medications and fat intake must be observed to prevent straining the liver. Of the right part of the liver is affected, the gallbladder may also be removed. Still if the removal of the gallbladder does not warrant a threat in one's life. But dietary modifications and changes in lifestyle would be necessary.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.