we retrospectively reviewed the radiological and clinical findings of 13 patients with a pathologically confirmed mesenchymal hamartoma of the liver .
the institutional review board approved the review of the radiological and clinical data for this study and waived the requirement for informed consent .
a computed hospital information system was used to identify all patients with a pathologically proved mesenchymal hamartoma during a 15-year period . the pathological diagnosis for a mesenchymal hamartoma
was based on overgrowth of the mesenchymal stroma and the proliferation of architecturally abnormal bile ducts with or without a cystic change , accompanied by periductal collaring of the stromal cells ( 1 , 9 ) .
three pediatric radiologists retrospectively reviewed the radiological features of the hepatic mesenchymal hamartomas by consensus .
ct scans were obtained with various third generation ct scanners at 80 - 120 ma , 100 - 120 kvp , and 5- to 10-mm thick sections .
ct scans were obtained after an intravenous bolus injection of contrast media and portal venous phase scans of the liver were available for all patients .
ct images of the tumor were evaluated for location , size , presence of septa within the cystic portion , ct attenuation of the tumor relative to the surrounding hepatic parenchyma ( low , iso , or high ) , pattern of contrast - enhancement ( homogeneous or heterogeneous enhancement of the solid portion , and septal enhancement of the cystic portion ) and presence of calcification on a pre - contrast ct scan . according to the extent of cystic component on the ct scans ,
we classified each tumor into one of three types : 1 ) multiseptated cystic - a purely cystic tumor with multiple thin septa ; 2 ) mixed cystic and solid - a partially cystic tumor with irregular thick septa ; 3 ) solid - a purely solid tumor without a cystic portion .
the cystic portion was defined as an area of low attenuation that showed 0 - 40 hounsfield units ( hu ) of ct attenuation value .
we classified the septal thickness as follows : thin ( < 2 mm in thickness ) or thick ( > 2 mm in thickness ) .
ultrasonographic ( us ) scans of nine patients were available for review . among them , seven patients had a color or power doppler us examination .
us images were evaluated for the presence of capsule , internal content of the cystic portion ( echogenic debris or fluid - fluid level ) , septal thickness within the cystic portion , and the echogenicity of the solid portion .
the amount of mesenchymal stroma , the presence or absence of duct proliferation , the amount of hepatocytes , and the presence or absence of vascular proliferation was evaluated .
the amount of mesenchymal stroma and hepatocytes were evaluated semi - quantitatively : little in < 10% of the mesenchymal hamartoma , moderate in 10 - 50% of the mesenchymal hamartoma and abundant in > 50% of the mesenchymal hamartoma .
the age of the patients , size of the tumor and various histological findings were compared with the imaging features of the hepatic mesenchymal hamartomas among the three ct types using the kruskall - wallis test .
chicago , il ) . a two - tailed p - value of < 0.05 was considered to be statistically significant .
we retrospectively reviewed the radiological and clinical findings of 13 patients with a pathologically confirmed mesenchymal hamartoma of the liver .
the institutional review board approved the review of the radiological and clinical data for this study and waived the requirement for informed consent .
a computed hospital information system was used to identify all patients with a pathologically proved mesenchymal hamartoma during a 15-year period . the pathological diagnosis for a mesenchymal hamartoma
was based on overgrowth of the mesenchymal stroma and the proliferation of architecturally abnormal bile ducts with or without a cystic change , accompanied by periductal collaring of the stromal cells ( 1 , 9 ) .
three pediatric radiologists retrospectively reviewed the radiological features of the hepatic mesenchymal hamartomas by consensus .
ct scans were obtained with various third generation ct scanners at 80 - 120 ma , 100 - 120 kvp , and 5- to 10-mm thick sections .
ct scans were obtained after an intravenous bolus injection of contrast media and portal venous phase scans of the liver were available for all patients .
ct images of the tumor were evaluated for location , size , presence of septa within the cystic portion , ct attenuation of the tumor relative to the surrounding hepatic parenchyma ( low , iso , or high ) , pattern of contrast - enhancement ( homogeneous or heterogeneous enhancement of the solid portion , and septal enhancement of the cystic portion ) and presence of calcification on a pre - contrast ct scan . according to the extent of cystic component on the ct scans ,
we classified each tumor into one of three types : 1 ) multiseptated cystic - a purely cystic tumor with multiple thin septa ; 2 ) mixed cystic and solid - a partially cystic tumor with irregular thick septa ; 3 ) solid - a purely solid tumor without a cystic portion .
the cystic portion was defined as an area of low attenuation that showed 0 - 40 hounsfield units ( hu ) of ct attenuation value .
we classified the septal thickness as follows : thin ( < 2 mm in thickness ) or thick ( > 2 mm in thickness ) .
ultrasonographic ( us ) scans of nine patients were available for review . among them , seven patients had a color or power doppler us examination .
us images were evaluated for the presence of capsule , internal content of the cystic portion ( echogenic debris or fluid - fluid level ) , septal thickness within the cystic portion , and the echogenicity of the solid portion .
the amount of mesenchymal stroma , the presence or absence of duct proliferation , the amount of hepatocytes , and the presence or absence of vascular proliferation was evaluated .
the amount of mesenchymal stroma and hepatocytes were evaluated semi - quantitatively : little in < 10% of the mesenchymal hamartoma , moderate in 10 - 50% of the mesenchymal hamartoma and abundant in > 50% of the mesenchymal hamartoma .
the age of the patients , size of the tumor and various histological findings were compared with the imaging features of the hepatic mesenchymal hamartomas among the three ct types using the kruskall - wallis test .
chicago , il ) . a two - tailed p - value of < 0.05 was considered to be statistically significant .
the subjects were seven boys and six girls , aged from 6 months to 7 years 6 months ( mean age : 3 years 2 months ) .
there was no significant difference of age ( p = 0.93 ) among the three ct types of tumors .
the patients presented with abdominal distension ( n = 8) , a palpable mass ( n = 3 ) or an incidentally detected tumor during us ( n = 2 ) for other clinical indications : a patient ( case 8) with peutz - jeghers syndrome , and a patient ( case 13 ) that had a kasai operation for biliary atresia at one month of age , respectively . the serum level of alpha - fetoprotein , total   and direct bilirubin level , alkaline phosphatase level , and level of transaminases ( aspartate transaminase and alanine transaminase ) were normal in all except two patients that had an elevated level of alpha - fetoprotein : the patient with biliary atresia ( case 13 ) and a 9-month - old girl ( case 5 ) .
the tumor occurred in the right lobe of the liver in nine patients and in the left lobe in four patients .
splenomegaly , ascites and retroperitoneal lymphadenopathy were noted in one patient that had biliary atresia .
the longest diameter of the tumors ranged from 1.8 to 20 cm ( mean 13.0 cm ) and was larger than 10 cm in 11 patients ( 85% ) .
there was no significant difference in the size of the tumors ( p = 0.79 ) among the three ct types of tumors .
1 ) , mixed solid and cystic in five patients ( 38% ) ( figs . 2 , 3 ) , and solid in four patients ( 31% ) ( figs . 4 , 5 ) . in four patients with a multiseptated cystic tumor , us ( n = 1 ) showed a well - defined tumor with variable cystic spaces and multiple thin septa in the liver ( fig .
all of these tumors showed fine enhancing septa within the cystic tumor on post - contrast ct ( fig .
neither calcification   nor a solid portion was detected in these patients . in five patients with a mixed cystic and solid tumor , us ( n
= 5 ) showed a well - defined tumor with variable - sized cystic spaces , irregularly thick septa , and a solid portion of variable extent with heterogeneous hyperechogenicity ( figs .
2a , 3a ) . in three patients , internal debris with fluid - fluid level was seen in the cystic portion of the tumor ( figs .
2a , 2c ) . on color and power doppler us ( n = 4 )
a tiny nodular intratumoral calcification was seen in one patient ( case 8) ( fig .
= 3 ) showed a well - defined , isoechoic tumor ( n = 1 ) or slightly hyperechoic ( n = 2 ) ( fig .
color or power doppler us   ( n = 3 ) showed central ( fig .
these tumors showed low attenuation on a pre - contrast ct scan in all patients , except for one with a high attenuating lesion . at post - contrast ct ,
4b , 5c ) . in the patient that had biliary atresia ( case 13 ) , the tumor appeared as a 1.8-cm sized enhancing nodule with a peripheral rim of low attenuation at post - contrast ct ( fig .
the mesenchymal hamartomas showed multiple variable sized cystic portions within the tumor in their gross morphology ( figs .
each mesenchymal hamartoma with a multiseptated cystic appearance contained various amounts of myxoid or collagenous stroma and showed proliferation of the malformed bile ducts with periductal collaring of the stromal cells ( fig .
all of the four patients with a multiseptated cystic tumor contained a small amount of hepatocytes ( < 10% ) on a semiquantitative evaluation .
the mesenchymal hamartomas with a mixed solid and cystic appearance also contained various amounts of myxoid or collagenous stroma and showed proliferation of the malformed bile ducts with periductal collaring of the stromal cells ( fig .
the amount of hepatocytes was small in three patients and moderate in two patients . in four patients with a solid mesenchymal hamartoma
, a moderate ( n = 3 ) amount or abundant amount ( n = 1 ) of hepatocytes was found in the cords , islands or lobular pattern .
the solid tumor also contained various amounts of mesenchymal stroma and proliferation of the small bile duct was seen ( fig .
4d ) . in one patient with an enhancing nodule with a peripheral rim of low attenuation ( case 13 ) , the enhancing portion revealed a large amount hepatocytes histologically with a rim of myxoid stroma .
the amount of hepatocytes was significantly different among the multiseptated cystic , mixed solid and cystic , and solid tumors ( p = 0.042 ) .
the other pathological findings such as the amount of mesenchymal stroma , the presence of a bile duct or vessel proliferation were not statistically significant among the three groups of the different imaging spectrum .
the subjects were seven boys and six girls , aged from 6 months to 7 years 6 months ( mean age : 3 years 2 months ) .
there was no significant difference of age ( p = 0.93 ) among the three ct types of tumors .
the patients presented with abdominal distension ( n = 8) , a palpable mass ( n = 3 ) or an incidentally detected tumor during us ( n = 2 ) for other clinical indications : a patient ( case 8) with peutz - jeghers syndrome , and a patient ( case 13 ) that had a kasai operation for biliary atresia at one month of age , respectively . the serum level of alpha - fetoprotein , total   and direct bilirubin level , alkaline phosphatase level , and level of transaminases ( aspartate transaminase and alanine transaminase ) were normal in all except two patients that had an elevated level of alpha - fetoprotein : the patient with biliary atresia ( case 13 ) and a 9-month - old girl ( case 5 ) .
the tumor occurred in the right lobe of the liver in nine patients and in the left lobe in four patients .
splenomegaly , ascites and retroperitoneal lymphadenopathy were noted in one patient that had biliary atresia .
the longest diameter of the tumors ranged from 1.8 to 20 cm ( mean 13.0 cm ) and was larger than 10 cm in 11 patients ( 85% ) .
there was no significant difference in the size of the tumors ( p = 0.79 ) among the three ct types of tumors .
1 ) , mixed solid and cystic in five patients ( 38% ) ( figs . 2 , 3 ) , and solid in four patients ( 31% ) ( figs . 4 , 5 ) . in four patients with a multiseptated cystic tumor , us ( n = 1 ) showed a well - defined tumor with variable cystic spaces and multiple thin septa in the liver ( fig .
all of these tumors showed fine enhancing septa within the cystic tumor on post - contrast ct ( fig .
neither calcification   nor a solid portion was detected in these patients . in five patients with a mixed cystic and solid tumor , us ( n
= 5 ) showed a well - defined tumor with variable - sized cystic spaces , irregularly thick septa , and a solid portion of variable extent with heterogeneous hyperechogenicity ( figs .
2a , 3a ) . in three patients , internal debris with fluid - fluid level was seen in the cystic portion of the tumor ( figs .
2a , 2c ) . on color and power doppler us ( n = 4 )
a tiny nodular intratumoral calcification was seen in one patient ( case 8) ( fig .
= 3 ) showed a well - defined , isoechoic tumor ( n = 1 ) or slightly hyperechoic ( n = 2 ) ( fig .
color or power doppler us   ( n = 3 ) showed central ( fig .
these tumors showed low attenuation on a pre - contrast ct scan in all patients , except for one with a high attenuating lesion . at post - contrast
4b , 5c ) . in the patient that had biliary atresia ( case 13 ) , the tumor appeared as a 1.8-cm sized enhancing nodule with a peripheral rim of low attenuation at post - contrast ct ( fig .
the mesenchymal hamartomas showed multiple variable sized cystic portions within the tumor in their gross morphology ( figs .
each mesenchymal hamartoma with a multiseptated cystic appearance contained various amounts of myxoid or collagenous stroma and showed proliferation of the malformed bile ducts with periductal collaring of the stromal cells ( fig .
all of the four patients with a multiseptated cystic tumor contained a small amount of hepatocytes ( < 10% ) on a semiquantitative evaluation .
the mesenchymal hamartomas with a mixed solid and cystic appearance also contained various amounts of myxoid or collagenous stroma and showed proliferation of the malformed bile ducts with periductal collaring of the stromal cells ( fig .
the amount of hepatocytes was small in three patients and moderate in two patients . in four patients with a solid mesenchymal hamartoma
, a moderate ( n = 3 ) amount or abundant amount ( n = 1 ) of hepatocytes was found in the cords , islands or lobular pattern .
the solid tumor also contained various amounts of mesenchymal stroma and proliferation of the small bile duct was seen ( fig .
4d ) . in one patient with an enhancing nodule with a peripheral rim of low attenuation ( case 13 )
, the enhancing portion revealed a large amount hepatocytes histologically with a rim of myxoid stroma .
the amount of hepatocytes was significantly different among the multiseptated cystic , mixed solid and cystic , and solid tumors ( p = 0.042 ) .
the other pathological findings such as the amount of mesenchymal stroma , the presence of a bile duct or vessel proliferation were not statistically significant among the three groups of the different imaging spectrum .
a mesenchymal hamartoma is the second most common benign hepatic tumor in children and accounts for 8% of all hepatic tumors in children ( 10 - 14 ) .
histologically , a mesenchymal hamartoma appears as a disordered arrangement of mesenchyme , bile ducts and hepatocytes ( 1 - 3 , 9 , 15 )
. cords of normal - appearing hepatocytes are separated by zones of loose poorly cellular mesenchyme .
cystic degeneration of the mesenchyme with resultant fluid accumulation from obstruction and dilatation of the lymphatics and/or by entrapped bile ducts may lead to enlargement of the tumor ( 12 ) .
the margin between the liver and the tumor is distinct ; however , a true capsule is generally not present ( 2 ) . the level of serum alpha - fetoprotein , which is believed to be secreted by the proliferating hepatocytes within the tumor , can be elevated ( 13 , 14 ) . a multiseptated cystic appearance , which may be a typical finding of mesenchymal hamartoma , is rarely seen in other hepatic tumors in children .
intratumoral calcification , which can be frequently detected in hepatoblastomas ( over 50% ) or infantile hemangioendotheliomas ( up to 40% ) ( 11 ) , has been reported very rarely for a mesenchymal hamartoma .
( 8) described the ct findings of a mesenchymal hamartoma containing central and peripheral calcifications in a 57-year - old woman .
( 15 ) also described the ct findings of the multiseptated cystic form of a mesenchymal hamartoma with a septal calcification in a 10-year - old boy . in this series
although a mesenchymal hamartoma present most frequently as a multiseptated cystic or mixed solid and cystic tumor ( 1 - 5 ) , it can rarely occur as a solid tumor ( 6 - 9 ) . in this study , according to the extent of the cystic component on ct scans , we classified each tumor into one of three types for evaluating the imaging spectrum of this tumor . in this study ,
the tumor was totally solid in 31% of the patients , and one case of a solid mesenchymal hamartoma ( case 11 ) showed features of a so - called " mixed hamartoma . "
the mixed hamartoma is a rare hamartomatous lesion composed of all cellular components of the normal liver , including a larger amount of hepatocytes , ductal proliferation , and hepatocellular - ductal transition .
the mixed hamartoma and mesenchymal hamartoma may be in one disease spectrum , since there is some overlapping in the histological features of both hamartomas ( 16 , 17 ) . in children with a solid mesenchymal hamartoma
, radiological differential diagnosis should include various hepatic tumors such as a hepatoblastoma , a hepatocellular carcinoma , an infantile hemangioendothelioma , a hepatic adenoma , or a focal nodular hyperplasia .
heterogeneous enhancement and absence of a tumor capsule in a mesenchymal hamartoma can be helpful in the differential diagnosis from other tumors . as in one of our patients that had biliary atresia and a solid mesenchymal hamartoma ( case 13 ) , lack
( 18 ) described a mesenchymal hamartoma in a 5-month - old girl with biliary atresia , which was found incidentally during an exploratory laparotomy for obstructive jaundice .
lack ( 18 ) showed an interest in this case because one of the theories for development of a mesenchymal hamartoma is biliary obstruction ( 19 ) . in conclusion ,
a mesenchymal hamartoma of the liver in children can show a wide spectrum of radiological features from a multiseptated cystic tumor to a mixed solid and cystic tumor , and even a solid tumor .
 objectivea hepatic mesenchymal hamartoma is an uncommon benign tumor in children and little is known about the spectrum of its radiological features . 
 the purpose of this study is to describe the spectrum of radiological features of a hepatic mesenchymal hamartoma in children.materials and methodsthirteen children with a pathologically confirmed hepatic mesenchymal hamartoma ( m : f = 7:6 ; mean age , 3 years 2 months ) were included in our study . ultrasonography ( us ) was performed in nine patients including color and power doppler us ( n = 7 ) . 
 ct scans were performed in all patients . 
 we evaluated the imaging findings of the hepatic mesenchymal hamartomas and the corresponding pathological features.resultseach patient had a single tumor ( mean diameter : 13 cm [ 1.8 - 20 cm ] ) . 
 on ct and/or us , four patients ( 31% ) had a " multiseptated cystic tumor " , five patients ( 38% ) had a " mixed solid and cystic tumor " , and four patients ( 31% ) had a " solid tumor . " 
 the septa of the cystic portion were thin in the multiseptated cystic tumors and irregularly thick in the mixed solid and cystic tumors as seen on us . on a post - contrast ct scan , solid portions or thick septa of the tumors showed heterogeneous enhancement . 
 the amount of hepatocytes was significantly different among the three tumor groups according to the imaging spectrum ( p = 0.042).conclusiona hepatic mesenchymal hamartoma in children can show a wide spectrum of radiological features , from a multiseptated cystic tumor to a mixed solid and cystic tumor , and even a solid tumor . 
MATERIALS AND METHODS
Subjects
Imaging and Analysis
Pathological Correlation
RESULTS
Clinical Findings
Imaging Characteristics
Pathological Correlation
DISCUSSION