Focular nodular hyperplasia is the most common benign tumour of the liver after the hemangiomas. It can be seen at any age and in both sexes, but is more frequent in women (ratio of 9:1) and in young people (between 20 and 50 years).
Currently the most usual way to diagnose it is through the findings of scans (abdominal ultrasound or abdominal CT scan) carried out for unrelated symptoms or for a check up.
Pathogenesis and histology
Focal nodular hyperplasia, also known as hamartoma, is regarded as a liver nodule of regenerative and not neoplastic type, in fact polyclonality of its cells has been demonstrated. The most accepted theory is that the lesion originates in the reaction of the hepatic parenchyma to the hypoperfusion produced by the anomalous artery which is generally found in the centre of the lesion.
Focal nodular hyperplasia generally consists of central scarring in the connective tissue where there is an artery disproportionately large for the size of the nodule. Hepatocytes of normal aspect, with sinusoids and Küpffer cells are observed. There can be proliferation of biliary ducts and the general aspect of the nodule tissue is similar to that of hepatic cirrhosis. There exists a variant called telangiectasic, which is usually multifocal and characteristically does not have central scarring.
Diagnosis
The diagnosis of focal nodular hyperplasia is based fundamentally on analysis of images and only in exceptional circumstances is it necessary to carry out histology by means of a biopsy or liver resection. The great majority of patients do not present any symptoms and the lesion is discovered because of investigations carried out for other reasons. In the rare cases in which there are associated symptoms, these are non-specific (pain, palpable mass, early fullness). The complications such as hemorrhage or infarct are anecdotal.
The following are the most used investigations:
- Ultrasound: This shows lesions of variable size, whether hypo, iso or hyperechogenic. The central scarring, when it is identified (20% of cases), can be highly suggestive of this diagnosis. The arterial type irrigation detected by Doppler helps to distinguish it from hepatic adenoma, which has a pattern of venous irrigation.
- CT Scan: Computerised axial tomography with helicoidal technology is one of the investigations which contributes most information. This can confirm the diagnosis by showing a nodule which is reinforced in the arterial phase. It shows central scarring, which later becomes isodense in the portal phase.
- MRI Scan: Nuclear magnetic resonance (MRI) scan, like CT scanning can be of great help in showing the typical vascular characteristics of focal nodular hyperplasia, in some studies reaching a very high specificity (98%), when typical characteristics are observed.
- Nuclear medicine: The schintograph with technetium is based on the focal nodular hyperplasia having Kűpffer cells which capture the colloid with injected technetium, allowing it to be differentiated from hepatic adenoma.
- Blood tests: Liver function tests (transaminases and tests of synthetic and excretory liver function) are usually normal, as is the alpha fetoprotein. Markers for hepatitis B and hepatitis C are normally requested.
The most important differential diagnosis considerations for hyperplasia are hepatic adenoma, hepatocellular carcinoma, hepatic hemangioma and hypervascular metastases.
Treatment and management
Owing to the fact that focal nodular hyperplasia is a non-neoplastic benign lesion and almost always asymptomatic, it does not usually require treatment. The size of the nodules remains stable over time. The most important aspect in its evaluation is the correct diagnosis, avoiding invasive examinations and treatments. Generally it is followed up by taking images of the lesion to show there has been no increase in size. It is important to keep in mind that for patients with focal nodular hyperplasia, surgery is only required in exceptional circumstances.
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