Benign liver lesions are common and are present in around 20% of the general population.  Benign liver lesions are by far the most common liver lesions seen, and once characterised usually do not require any further surveillance or treatment.  However, if liver lesions cause pain, increase in size, can’t be confidently characterised by radiological imaging they may need to be surgically removed.

Hepatic Hemangioma

Hemangioma are the most common type of benign liver lesion.  They are said to be present in around 1/20 adults.  An hepatic hemangioma is an abnormal mass of blood vessels. They are usually identified incidentally and are asymptomatic. They very rarely require surgical intervention, however, they can easily be mistaken for other malignant lesions so require careful characterisation by radiological imaging with expertise in liver imaging.

Hepatic Adenoma

Hepatic adenoma are uncommon benign liver lesions.  They are most commonly found in women who regularly take the oestrogen containing oral contraceptive pill, or in athletes taking anabolic steroids. Depending upon their subtype they may have increased risk of malignant progression or bleeding.  It is therefore important to differentiate them from other liver lesions, and occasionally it may be necessary to obtain tissue either by surgical resection or radiologically guided biopsy to subtype the lesion and determine treatment plan.

Focal Nodular hyperplasia (FNH)

Focal nodular hyperplasia of the liver is the second most common solid benign liver lesion. FNH are almost always asymptomatic; however, some patients may experience abdominal pain and mild gastro-intestinal (GI) discomfort, if the lesion is adjacent to the liver capsule.  FNH is benign, and not associated with any risk, however it is important that they are differentiated from other liver lesions.   FNH can be difficult to distinguish from hepatic adenoma or the fibrolamellar variant of hepatocellular carcinoma, a rare primary liver malignancy. Careful diagnosis with multiphase CT and/or MRI is usually required to avoid unnecessary biopsy or surgery.  Once characterised, FNH rarely requires ongoing surveillance or treatment.

Hepatic Cysts

Liver cysts are thin-walled structures within the liver that contain fluid.  They occur in approximately 5% of the population, and are usually incidentally found on imaging by ultrasound, CT or MRI.  Only 5% of patients with liver cysts develop symptoms. The symptoms associated with liver cysts include upper abdominal fullness, discomfort, or pain.  Treatment of simple symptomatic liver cysts involves removing a large portion of the cyst wall (fenestration).  This can usually be done laparoscopically (key-hole surgery).  Aspiration of the fluid from the cyst is ineffective because the fluid reaccumulates within days.  

Complex cysts, contain both solid and cystic components.  They can be the result of infection with echinococcus tapeworm or tumour.  Primary cystic tumours of the liver are extremely rare and are either cystadenoma (benign) or cystadenocarcinoma (malignant).    Because of the risk of malignancy, complex cystic tumours usually require surgical removal (resection).