Benign liver masses
- Lesion
Most liver masses found by chance in healthy livers are harmless, such as hemangiomas and focal nodular hyperplasia.
What it is
Many liver masses are not neoplasms. Focal nodular hyperplasia is a hyperplastic response of hepatocytes to an abnormal artery, with a central stellate scar. Cavernous hemangioma, the most common benign liver tumour, is a vascular lesion. Nodular regenerative hyperplasia, large regenerative nodules, bile duct adenomas, von Meyenburg complexes, abscesses, granulomas and inflammatory pseudotumours can all mimic a tumour. Correct naming avoids needless surgery.
Step by step
- FNH: a congenital or acquired arterial malformation sends excess arterial flow to one area.
- Hepatocytes respond by polyclonal hyperplasia, forming nodules around the artery.
- Fibrous septa radiate from the abnormal vessel: the central stellate scar.
- Hemangioma: a vascular malformation grows slowly by filling and dilating channels.
- Altered blood flow also explains nodular regenerative hyperplasia: alternating atrophy and regeneration.
Benign liver masses
| Lesion | Gross and microscopy | Key point |
|---|---|---|
| Cavernous hemangioma | Well-defined red-blue soft mass; vascular spaces lined by endothelium, fibrous walls | Most common; usually incidental |
| Focal nodular hyperplasia | Tan nodule with central stellate scar; hepatocyte nodules, thick-walled arteries, ductular reaction in septa | Not neoplastic; map-like glutamine synthetase staining |
| Nodular regenerative hyperplasia | Diffuse small nodules without fibrous septa | Portal hypertension; reticulin stain shows it |
| Bile duct adenoma or hamartoma | Small subcapsular white nodules of bland ductules | Mimics metastasis at surgery |
| Inflammatory pseudotumour, abscess, granuloma | Inflammatory masses | Clinical and biopsy correlation |
Markers
- Glutamine synthetase (map-like in FNH)
- Reticulin
- CD34 and CD31 (vessels)
Test yourself
Think of the answer, then tap the question to see it.
What is the most common benign tumour of the liver?
Cavernous hemangioma.
What is the characteristic gross feature of focal nodular hyperplasia?
A central stellate fibrous scar containing large abnormal arteries, with radiating septa.
Why is nodular regenerative hyperplasia easy to miss on H&E?
Nodules have no fibrous septa; a reticulin stain is needed to see the compressed plates around regenerating nodules.
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Hepatic hemangioma: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.