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Hepatic mesenchymal hamartoma

A hepatic mesenchymal hamartoma is an uncommon benign hepatic tumour. Some authors even consider this to be a developmental anomaly rather than a cystic neoplasm 9,12.

Epidemiology 

It typically occurs in children and neonates with most cases presenting within the first two years of life 3. Male predominance (2:1)13.

Clinical presentation

Abdominal enlargement and respiratory distress are thought to be the the most common presenting features in children. They can very rarely present in adults 10.

Pathology

The lesions are characterised by an admixture of ductal structures (blood vessels, small groups of hepatocytes, and bile ducts) within a copious loose / oedematous connective tissue stroma 7-8

On a cut surface, there are typically multiple cysts in an oedematous stroma; the cysts
can vary in size ranging from a few millimeters to 16 cm, and in number and distribution - being discrete or connected13.

Mesenchymal hamartomas in adults may show a series of histologic modifications -
i.e, progressive loss of hepatocytes, degeneration of bile duct epithelium,
and cystic changes of the mesenchymal component  12-13.

Radiographic features

General

Mesenchymal hamartomas can show a wide spectrum of radiological features, from being a multiseptated cystic tumour to a mixed solid and cystic tumour to even a completely solid tumour 1.

The dominant radiographic patten is a however a large (often around 12 - 15cm 8), predominantly cystic mass with internal septations 3. There can be considerable variation in the size of septae and cystic spaces 9.

Plain film

Although non diagnostic, plain films may show a large, non-calcified mass in the right upper quadrant 9.

Ultrasound

It usually appear as a multiple septa cystic lesion interspersed with solid components. Detection is difficult for pedunculated lesions. In some lesions may be the predominance of solid structures13.

CT

On unenhanced CT,  it usually has a heterogeneous appearance. The stromal elements often appear hypo-attenuating, whereas the cystic components have water attenuation 8-9. The appearance of cystic and solid portions has been likened to swiss cheese.

On a post-contrast CT scan, solid portions or thick septa of the tumours can show heterogeneous enhancement 1-8; 13.

MRI

MR imaging appearance of mesenchymal hamartoma can also vary dependant on the presence of stromal elements as well as protein content of the fluid 8.

DSA - angiography

While not being a standard diagnostic imaging modality of choice, angiography may   show peripheral hypervascularity to the lesion with a septated avascular center 3-9.

Complications

There are fatal complications associated with a hepatic masenchymal hamartoma (particularly in the pre-natal group). These generally result from the size of lesion and include 2.

Treatment and prognosis

Mesenchymal hamartomas are benign lesions and are best treated by surgical resection, which usually results in cure 2. There are occasional reports of where ultrasound-guided intra-operative aspiration of fluid from the cystic components of the tumour to reduce its volume facilitating surgical resection 5.

Differential diagnosis

See also

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