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| Discussion |
Case Report: A 13-months-old male child presented with gradual distention of abdomen over a period of 25 days with fever and cough since four days. On physical examination, the patient was afebrile and anicteric. There was fullness in the right upper quadrant of the abdomen due to hepatomegaly . No other significant finding was detected on physical examination.
Laboratory investigation: SGPT- 22U/L, SGOT-42U/L, Total bilirubin- 0.54mg%, BUN- 11mg%, Hb- 9.3gm%, Serum Alfa fetoprotein- 9.81ng/ml ( normal range- 0 to 13.4 ng/ml), Beta HCG-absent.
An ultrasound examination of the abdomen (Figs 1,2) revealed a large 10.5 x 9.5 x 10 cm sized anechoic cystic mass occupying almost the entire right lobe of the liver. There were multiple internal septations within. However, no solid component or vascularity within it was seen. The left lobe of the liver was enlarged. The portal vein showed normal flow; its right branch splayed over it anterosuperiorly. No portal or retroperitoneal lymphadenopathy was seen nor was there ascitis. The rest of the abdomino-pelvic ultrasound examination was normal .
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Fig: 1 |
Fig: 2 |
A plain and contrast enhanced CT of the abdomen (Figs. 3,4,5) confirmed the USG findings and showed a large well-defined cystic mass with few internal septations in the right lobe of liver measuring approximately 10 x 8 x 13cms occupying segments VII , VIII and VI. There was no calcification, nor was there any soft tissue component with in. On contrast scan, the septae showed enhancement.
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Fig: 3 |
Fig. 4 |
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The mass was seen to displace the middle hepatic vein; the right hepatic vein was not visualised and the left hepatic vein was normal. The transhepatic IVC was compressed. The mass was abutting the portal vein bifurcation. The main portal vein at the porta and its left branch were normal. The anterior branch of the right portal vein was displaced by the mass forming its anterior margin. The posterior branch of the right portal vein was not seen. The hepatic artery was not hypertrophied. The rest of abdomen was unremarkable.
On MRI (figs 6-11), the lesion was hyperintense on T2W image and hypointense on T1W image -conforming its cystic nature. Multiple septa were best seen on T2 W images which demonstrated the complex nature of the cystic mass.
These features suggested a diagnosis of benign mesenchymal hamartoma of the liver.
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Fig: 6 |
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Fig: 11 |
Mesenchymal hamartomas are uncommon and account for only 8% of all childhood liver masses. This lesion, though uncommon, is the second most common benign liver tumor of the pediatric age.
Age and presentation: It occurs exclusively during infancy and childhood although few cases in older age groups have been reported. A majority of the cases present at a mean age of 16 months, the range being from newborn to five years of age. The origin is mostly from the right lobe of the liver. There is slight male predominance. Most of the cases remain asymptomatic while others are detected incidentally. The most common clinical presentation is with a right upper quadrant mass, respiratory distress, fever and raised right hemidiaphragm. Occasionally, sudden enlargement may result from rapid fluid accumulation in the cysts. Mass effect from a bulky tumour may cause respiratory distress and lower extremity edema due to compression of the IVC.
Benign liver tumors in children may be divided into two major groups:- those of epithelial derivation, including simple cysts, focal nodular hyperplasia and adenomas and those of mesenchymal derivation including hamartomas and hemangiomas. Benign mesenchymal tumors of the liver are more common than their epithelial counterparts.
A mesenchymal hamartoma is a benign cystic developmental lesion consisting of gelatinous mesenchymal tissue with cyst formation and remnants of normal hepatic parenchyma. It is a large tumor, usually of size 15cm or more at diagnosis, with cysts present in 80% of cases. It is a well-defined tumor that may be encapsulated or pedunculated.
On cut section, this tumor may either have mesenchymal predominance (a solid appearance) or cystic predominance (multiloculated cystic masses).
Microscopically, it consists of cysts, remnants of portal traids, hepatocytes, and fluid filled mesenchyme.
Liver function tests usually remain within normal limits. Tumor markers are negative.
On CT, mesenchymal hamartomas appear as well-defined masses with central area of low density and internal septations. Both solid and cystic areas are seen.
The MR appearances of mesenchymal hamartomas depend on their mesenchymal (stromal) or cystic predominance. Lesions with mesenchymal predominance have lower intensity than normal liver on T2W images because of the fibrotic tissue content. Cystic predominant lesions are of variable intensity on T1W images and are significantly hyperintense on T2W images because of the cystic component.
Multiple septae are best seen on T2W images, which demonstrates the complex nature of the cystic mass.
Extensive surgery is not necessary because mesenchymal hamartomas are not “true” neoplasms, but a failure of normal development - thus, simple excision, marsupialization, or incisional drainage is all that is required.
Differential diagnosis:
Vascular lesions of mesenchymal origin are hemangioendothelioma and cavernous hemangioma. Hemangioendothelioma usually presents before six months of age and is more common in females. It may be asymptomatic or presents as hepatomegaly, abdominal mass or high output cardiac failure. On CT scan, hypodense well defined homogenous masses are seen with calcification being seen in 40% of cases. Early peripheral enhancement with gradual central filling is evident. Cavernous hemangioma occurs in all age groups and is often asymptomatic and discovered incidentally. It is usually a solitary lesion with predilection for the right lobe and female population. On CT scan, it is seen as a hypodense to isodense well defined mass. On contrast enhancement, early dense, peripheral nodular enhancement with later centripetal fill is noted.
In contrast, simple non-parasitic cyst is solitary which may be very large with lining of columnar, cuboidal or flattened epithelium. The wall is thin and composed of mature connective tissue. Simple cysts may also show calcification.
Polycystic liver disease on the other hand is frequently associated with polycystic kidneys in about 50% of the patients. Frequently, there is cystic disease of other organs including spleen, pancreas, ovaries and lungs. The cysts may be scattered diffusely or restricted to one lobe – usually the left. Hepatic function is excellent as liver cells are preserved. CT scan is useful in diagnosing the lesion as it does not show enhancement with intravenous contrast. It may remain asymptomatic - although portal hypertension is common in the infantile variety. Symptomatic patients are usually in the 4th or 5th decade and symptoms are often due to associated polycystic kidneys.