hepatic angiomyolipoma ( aml ) , a tumor of the liver , is much rarer compared with its renal counterpart . amls are composed of the three following components : smooth muscle cells , adipocytes , and blood vessels . initial documentation of this disease was by ishak   in 1976 , and approximately three hundred cases have been reported in the english literature [ 2 , 3 , 4 , 5 , 6 , 7 ] . epithelioid aml was first described in the kidney by pea et al .   in 1991 as a peculiar variant of aml . the term epithelioid is applied when one of the three components , such as smooth muscle cells , become relatively rounded and rich in cytoplasm . only a few cases of hepatic epithelioid aml have been reported [ 3 , 9 ] . epithelioid aml has been demonstrated to express e - cadherin   and -catenin   as well as classical markers of melanocytic and myogenic differentiation such as hmb45 and sma . many cases of ruptured renal aml have been documented in the past ; however , ruptured hepatic aml are considered to be extremely rare . we present a rare case of ruptured hepatic epithelioid aml in a patient admitted for abdominal pain . a 38-year - old male was admitted to the emergency room with upper abdominal pain . laboratory findings revealed an abnormal liver function ( aspartate aminotransferase , 222 iu / l ; alanine aminotransferase , 158 iu / l ) . contrast - enhanced computed tomography ( ct ) revealed a large tumor in the posterior segment of the right hepatic lobe ( s6,7 ) . the tumor , measuring 10.5  9.5  7.0 cm in size , had heterogeneous components , with low - density areas corresponding to fat . it had ruptured into the space between the liver and the diaphragm at the upper surface of the posterosuperior segment of the right hepatic lobe ( s7 ) , with extravasation of contrast medium into a hematoma ( fig . however , he suddenly developed fever , and elevation of white blood cell count ( 22.0  10/l ) and c - reactive protein ( 21.9 mg / dl ) was detected . the hematoma surrounding the liver was drained , and although this hematoma was suspected of infection , it tested negative for bacterial infection . although infection was not confirmed , surgical resection was planned considering the possibility of infection . on preoperative contrast - enhanced ct , a thickened fibrous capsule had formed around the hematoma ( fig . in the reconstructed image of the sagittal section , it was easy to detect the ruptured point of the tumor ( fig . right lobectomy was performed , and the postoperative course was uneventful , with no sign of a tuberous sclerosis complex ( tsc ) or renal tumor . the surgically resected specimen contained a ruptured tumor , which appeared extensively hemorrhagic and with no macroscopically appreciable fat component ( fig . triphasic elements , epithelioid tumor cells ( 5060% ) , mature fat ( 4050% ) , and thickened - wall blood vessels , were observed ( fig . a high - power view of the epithelioid cells displayed rounded or polygonal shape with abundant cytoplasm ( fig . 3c , d ) , molecules playing a role in cell - to - cell adhesion . even though epithelioid cells with enlarged or bizarre nuclei were intermingled , ki-67 ( mib-1)-positive cells accounted for < 1% . therefore the cause of the rupture could not be found despite careful macroscopic and microscopic examinations . aml of the liver is a much rarer neoplasm than that of the kidney . given that 4050% of patients with renal aml have tsc , association of hepatic aml with tsc is less frequent ( 625% of cases ) . one of the definitions of epithelioid aml in the kidney is that epithelioid cells occupy > 10% of the tumor ; their membranous positivity for e - cadherin   and -catenin   has been documented . in the present case , the epithelioid cell component occupied 5060% of the tumor , and e - cadherin and -catenin were weakly positive in a membranous pattern . therefore , applying the renal standard , this case could be appreciated as epithelioid aml of the liver . histological factors predicting the malignant progression of renal epithelioid aml , such as cellular atypia 70% of epithelioid cells , > 2 mitotic figures per 10 hpfs , atypical mitoses , and necrosis that were proposed by brimo et al . , were not found in this case . critical differences between renal and hepatic amls are not known ; therefore , the hepatic epithelioid aml observed in the present case was treated as benign . however , careful follow - up is required because of the lack of reliable data regarding the malignant progression of hepatic epithelioid amls . to the best of our knowledge , only five cases of ruptured hepatic amls have been reported in the english literature [ 3 , 9 , 16 , 17 , 18 ] ( table 1 ) . tumor size ( 4 cm ) and intratumoral aneurysm ( 5 mm ) are important factors predicting the rupture of renal amls . the latter is probably influenced by the former because tumor growth increases internal blood flow , which leads to blood vessel dilatation and aneurysm formation . the blood vessels of amls may be vulnerable in nature because of their architectural abnormality . using statistical analysis , the crucial cause of the rupture has been suggested to be the formation of an internal aneurysm . adopting this feature to hepatic aml , in the present case , tumor size well exceeded 4 cm , meeting the criterion for the risk of rupture . however , no aneurysm was found by angiography at the time of transcatheter arterial embolization and pathological examination . we described a case of ruptured hepatic aml , which is , to the best of our knowledge , the sixth reported case .
a 38-year - old male was admitted to our hospital due to upper abdominal pain . 
 computed tomography revealed a hepatic angiomyolipoma ( aml ; 10.5  9.5  7.0 cm in size ) , which had ruptured into the space between the liver and the diaphragm . 
 following transcatheter arterial embolization , surgical resection was performed . 
 the tumor consisted of epithelioid cells ( 5060% ) , mature fat ( 4050% ) , and thickened - wall blood vessels . 
 considering the amount of epithelioid cells and their positivity for e - cadherin and -catenin , the tumor was diagnosed as hepatic epithelioid aml . 
 cases of ruptured hepatic aml are rare . to the best of our knowledge , 
 this is the sixth case reported in the english literature .