Focal nodular hyperplasia and hepatocellular adenoma
Focal nodular hyperplasia and hepatocellular adenoma are both benign solid liver lesions, both found most often in women, and both frequently discovered by accident. They are grouped together here because distinguishing between them is the central clinical task — they look superficially similar but behave entirely differently, and the management of one is observation while the management of the other may be an operation.
How they form
Focal nodular hyperplasia
FNH is not a tumour at all in the usual sense. It is a localised overgrowth of otherwise normal liver tissue in response to an abnormal artery. A congenital arterial malformation delivers an excess of blood to one area of liver; the tissue responds by proliferating around it; and the result is a nodule of normal liver cells, bile ducts and supporting tissue arranged around a central fibrous scar containing that feeding artery.
This explains its behaviour. Because it is composed of normal liver cells, FNH has no malignant potential whatsoever. Because its architecture includes bile ducts and Kupffer cells, it takes up liver-specific contrast agents on MRI — the feature that allows it to be identified with confidence. And because the central scar is the anatomical signature of the feeding artery, that scar is what radiologists look for.
Hepatocellular adenoma
An adenoma is a true benign tumour: a clonal proliferation of liver cells, forming sheets without the normal architecture. It lacks bile ducts and has an abnormal blood supply, with fragile vessels running through it and no supporting framework — which is why, unlike FNH, it can bleed.
Adenomas are strongly associated with oestrogen exposure, and their incidence rose alongside the use of the combined oral contraceptive pill. They are also associated with anabolic steroid use, obesity and metabolic syndrome, and with certain glycogen storage diseases. Several molecular subtypes are now recognised, and these carry different risks — in particular the beta-catenin activated subtype, which has a higher risk of malignant change.
Symptoms
Both are usually silent. Larger lesions of either type may cause upper abdominal discomfort. The important difference is that an adenoma may present acutely with sudden severe pain from bleeding into the lesion or, less often, rupture with bleeding into the abdomen. FNH does not do this.
How the diagnosis is made
Contrast-enhanced MRI, ideally with a hepatocyte-specific contrast agent, is the key investigation. FNH retains this contrast in the delayed phase because it contains functioning liver cells and bile ducts; an adenoma does not. This single distinction resolves most cases.
Supporting features: FNH typically shows a central scar and homogeneous arterial enhancement; an adenoma is more heterogeneous, may contain fat or areas of haemorrhage, and lacks a true central scar.
Biopsy is reserved for cases where imaging cannot distinguish the two, or where subtyping an adenoma would change management. It carries a bleeding risk in a vascular lesion and is not used routinely.
A careful history matters: oral contraceptive use and its duration, anabolic steroid use, and any family history of glycogen storage disease all shift the probability.
Management — focal nodular hyperplasia
Once the diagnosis is confident, FNH requires no treatment. It does not become malignant, it does not bleed, and it does not need surveillance. Contraception does not need to be stopped and pregnancy is not contraindicated. Surgery is reserved for the uncommon case of genuinely disabling symptoms clearly attributable to a large lesion, or diagnostic uncertainty that cannot be resolved any other way.
The most valuable part of managing FNH is a confident diagnosis and a clear explanation, which spares the patient years of unnecessary scans.
Management — hepatocellular adenoma
Management is more active, and depends on size, sex and subtype.
- Stop the stimulus. Discontinuing the oral contraceptive pill or anabolic steroids, and weight loss where relevant, causes many adenomas to shrink. Imaging is repeated after an interval to assess response.
- Size matters. Lesions that remain above approximately five centimetres after stopping hormonal stimulation are generally considered for resection, because the risks of bleeding and of malignant transformation both rise with size.
- Sex matters. Adenomas in men carry a substantially higher risk of malignant change and resection is generally advised regardless of size.
- Subtype matters. Where a beta-catenin activated adenoma is identified, resection is favoured.
- Pregnancy requires individual discussion, as hormonal changes may promote growth. Many women with small adenomas proceed with pregnancy under imaging surveillance.
These are the accepted thresholds and serve as a starting point rather than a rule. In practice the decision is individualised: the position of the lesion, whether it can be removed with a minor rather than a major resection, the patient's age and plans regarding pregnancy, their general fitness, and their own view of living with an untreated lesion all shift the balance. Two patients with the same five-centimetre adenoma may reasonably be advised differently.
Treatment options
Resection is the definitive treatment, by laparoscopic, robotic or open approach according to the position and size of the lesion and the patient's circumstances. For a bleeding adenoma presenting acutely, arterial embolisation is often the first step to control haemorrhage, with resection performed later once the patient is stable and the anatomy clear.
Recovery
Recovery after liver resection for a benign lesion depends on the extent of resection and the approach. A laparoscopic segmental resection typically involves two to four days in hospital and a return to ordinary activity within two to three weeks; a larger open resection, six to eight weeks. Liver function is preserved because the remaining liver is healthy and regenerates.
Follow-up
None required after resection of FNH. After treatment of an adenoma, imaging follow-up is arranged, since further adenomas may develop in patients with multiple lesions or an ongoing predisposing factor. For adenomas managed without surgery, regular imaging is essential.
When to seek a surgical opinion
Any solid liver lesion that has not been confidently characterised warrants specialist review, because the distinction between FNH and adenoma changes everything that follows. An opinion is also worthwhile for any adenoma over five centimetres, any adenoma in a man, and any lesion that has grown or bled.
Common questions
What is the difference between these two lesions?
Focal nodular hyperplasia is not a tumour at all — it is normal liver tissue that has overgrown around an abnormal artery. It is harmless, does not bleed and does not become cancer, and it essentially never needs treating. A hepatocellular adenoma is a true benign tumour, and although also benign, it can bleed and a minority can transform into cancer, so it is managed more actively.
Why does it matter which one I have?
Because one needs nothing and the other may need treatment. Telling them apart is done with a specific type of MRI using a liver-specific contrast agent, which shows a characteristic pattern in each. Getting this right avoids both unnecessary surgery and missed risk.
Should I stop the contraceptive pill?
If you have an adenoma, yes — oestrogen drives their growth, and stopping hormonal contraception causes a proportion to shrink, sometimes substantially, over six to twelve months. For focal nodular hyperplasia there is no need to stop it.
Why does size matter so much for an adenoma?
Because both the risk of bleeding and the risk of turning into cancer rise with size, and the threshold generally used is five centimetres. Below that, in a woman who has stopped hormonal contraception, watching is usually appropriate. Above it, or if it grows, removal is advised.
Why is the advice different for men?
Because adenomas in men carry a considerably higher risk of malignant transformation, whatever their size. For that reason, removal is generally recommended for men regardless of how large the lesion is.
Can I become pregnant?
This needs individual discussion. Pregnancy raises oestrogen levels and can cause an adenoma to enlarge, with a risk of bleeding, so larger lesions are usually dealt with before a planned pregnancy. Smaller ones may be monitored with ultrasound during pregnancy. Focal nodular hyperplasia poses no problem in pregnancy.
I have been told my adenoma has a particular subtype. What does that mean?
Adenomas fall into several types with different behaviour. One type — associated with a gene called beta-catenin — carries a higher risk of becoming cancer and is removed regardless of size. Another, the inflammatory type, is more prone to bleeding and is associated with obesity and alcohol. Knowing the subtype refines the advice considerably.
Does weight matter?
Yes. Obesity and metabolic syndrome are associated with adenomas, particularly the inflammatory type, and weight loss can cause them to shrink. It is one of the few things within your control that genuinely alters the course.
Related conditions
Other conditions of the liver covered on this site:
- Liver cysts (simple hepatic cysts)
- Hydatid (echinococcal) cyst of the liver
- Liver haemangioma
- Liver abscess
- Hepatocellular carcinoma (HCC)
- Intrahepatic cholangiocarcinoma
- Liver metastases
This page provides general information and does not replace an individual medical consultation. Assessment and treatment are decided for each patient after review of their history, examination and imaging.