Hepatic mesenchymal hamartoma
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.
It typically occurs in children and neonates, with most cases presenting within the first two years of life 3. There is a male predominance (2:1) 13.
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.
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 connected 13.
Mesenchymal hamartomas in adults may show a series of histologic modifications: progressive loss of hepatocytes, degeneration of bile duct epithelium, and cystic changes of the mesenchymal component 12-13.
Mesenchymal hamartomas can show a wide spectrum of radiological features, from being a predominantly cystic tumour, to a multiseptated cystic tumour, to a mixed solid and cystic tumour, to even a completely solid tumour 1.
The dominant radiographic pattern, however, is a large (often around 12-15 cm 8), predominantly cystic mass with internal septations 3. There can be considerable variation in the size of septae and cystic spaces 9.
Although nonspecific, radiographs may show a large, noncalcified mass in the right upper quadrant 9.
It usually appear as a multiseptated cystic lesion interspersed with solid components. Detection is difficult for pedunculated lesions. In some lesions may be the predominance of solid structures 13.
On unenhanced CT, it usually has a heterogeneous appearance. The stromal elements often appear hypoattenuating, whereas the cystic components have water attenuation 8-9. The appearance of cystic and solid portions has been likened to swiss cheese.
On a postcontrast CT scan, solid portions or thick septa of the tumours can show heterogeneous enhancement 1-8,13.
- prominent cystic components
- multifocality is uncommon
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.
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.
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 ultrasound-guided intraoperative aspiration of fluid from the cystic components of the tumour to reduce its volume, facilitating surgical resection 5.
There are fatal complications associated with hepatic mesenchymal hamartomas (particularly in the prenatal group) that generally result from the size of lesion 2:
- fetal hydrops
- respiratory distress: neonatal respiratory distress
- circulatory complications/compromise owing to a large space-occupying abdominal lesion
On imaging consider
- hepatic abscess
- hepatoblastoma (especially when there is a predominance of the solid component and no increase in alpha-fetoprotein)
- hepatic embryonal sarcoma
- infantile hemangioendothelioma of liver
- simple hepatic cyst (or cluster): no solid compoment
- fetal tumours
- benign liver tumours in infants and children
- mesenchymal hamartomas of the chest wall
- undifferentiated (embryonal) sarcoma of the liver: malignant mesenchymal hepatic tumour
- depositional disorders
- infection and inflammation
- liver abscess
- hepatic hydatid infection
- liver and intrahepatic bile duct tumours
- benign epithelial tumours
- hepatic regenerative nodule
- focal nodular hyperplasia
- hepatocellular adenoma
- hepatic/biliary cysts
- hepatocellular hyperplasia
- benign nonepithelial tumours
- primary malignant epithelial tumours
- primary malignant nonepithelial tumours
- hematopoeietic and lymphoid tumours
- secondary tumours
- adrenal rest tumours
- hepatic carcinosarcoma
- hepatic fibroma
- hepatic Kaposi sarcoma
- hepatic lipoma
- hepatic mesenchymal hamartoma
- hepatic myxoma
- hepatic rhabdoid tumour
- hepatic solitary fibrous tumour
- hepatic teratoma
- hepatic yolk sac tumour
- inflammatory myofibroblastic tumor (inflammatory pseudotumor)
- nodular regenerative hyperplasia
- pancreatic rest tumours
- primary hepatic carcinoid
- benign epithelial tumours
- extrahepatic bile duct tumours
- liver and intrahepatic bile duct tumours
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- 13. GASTROINTESTINAL. ISBN:8535231439. Read it at Google Books - Find it at Amazon