adenomatoid tumors were first described by golden and ash1 and denoted the benign , often incidental , and typically well - circumscribed neoplasms of mesothelial origin.2 they occur mostly in the genital tract during a patient 's reproductive age , although extragenital adenomatoid tumors have rarely been reported in various organs including the adrenal gland , heart , mediastinum , appendix , liver , pancreas , peritoneum , and pleura.3 - 5 we report a case of a large , hepatic adenomatoid tumor that was combined with a small cavernous hemangioma . a 45-year - old canadian man had been followed regularly at the local hospital because of a liver mass detected on abdominal ultrasonography and computed tomography ( ct ) scan four years previously . at the time of the first diagnosis , the liver had hypervascular features with a lobular and cystic portion seen on ct scanning , and which was regarded as a cavernous liver hemangioma . three years later , he was transferred to our institute for further evaluation of his right upper quadrant pain . on the physical examination routine laboratory tests including cbc , liver battery , and coagulation tests were within normal ranges . a serologic test was negative for both the hepatitis b virus surface antigen and hepatitis c virus antibody . tumor markers such as -fetoprotein , protein induced by vitamin k absence - ii ( pivka - ii ) , carcinoembryonic antigen ( cea ) , and carbohydrate antigen 19 - 9 ( ca 19 - 9 ) were also within a normal range . on liver dynamic ct , the mass in segments iv and viii , and measuring 6.55.3 cm was hypervascular and showed intratumoral cystic change and calcification . there was another enhanced mass measuring 2.3 cm in the right hepatic dome and that was thought to be a hepatic hemangioma . the large hepatic mass was enhanced on arterial phase imaging of liver dynamic ct scan , but was not washed out in either early portal phase or delayed phase imaging ( fig . the liver mass was a well - defined , hypointense , solid mass on t1-weighted imaging and was hyperintense on t2-weighted imaging of mri scan ; there were multi - lobulated , cystic areas within the mass seen on mri . following enhancement with gadolinium - eob - dtpa , the mass appeared hypervascular on the arterial phase and showed decreased enhancement on the delayed phase ( fig . besides , there had been a renal cortical cyst which size was increased from 1.4 cm to 3.0 cm during 4 years of followup , but it was regarded as a simple benign cyst by imaging study . a preoperative liver core biopsy was performed , because a definitive diagnosis was not made . since a malignancy could not be completely excluded and the patient had presented with right upper quadrant pain , partial hepatectomy of segments iv and viii was performed . preoperative liver biopsy showed multifocal proliferation of clear , cuboidal cells in a tubular and cystic structure and highly vascular edematous stroma . because the clear cells were positive for cytokeratin and vimentin , metatstatic renal cell carcinoma was considered , although the tumor cells were negative for cd10 that is used as a marker for clear cell , renal cell carcinoma . the resected liver showed a solid mass measuring 7.56.53.7 cm and with a well - circumscribed border that was continuous with the glisson 's capsule and pushing the hepatic parenchyma . the mass was mostly solid , partly myxoid and hemorrhagic , and partly cystic with multiple , various sized cysts ( fig . 1f ) . the cut surface of the solid portion of the mass was mostly whitish - yellow , partly reddish , smooth , and glistening . microscopically , the tumor showed proliferation of flattened or cuboidal epithelioid cells in tubular or glandular structures as well as highly vascular stroma with thin - walled blood vessels ( fig . the epithelioid cells were diffusely positive for cytokeratin ( ae1/ae3 ) , vimentin , calretinin , and cytokeratin 5/6 , were focally positive for cd10 , and were negative for wt1 and cd34 ( fig . 3 ) . these findings support the mesothelial differentiation of the tumor cells . apart from this mass , there was an hepatic mass , measuring 2 cm in diameter and located in the right hepatic dome ; the mass was a typical , cavernous hemangioma ( fig . preoperative liver biopsy showed multifocal proliferation of clear , cuboidal cells in a tubular and cystic structure and highly vascular edematous stroma . because the clear cells were positive for cytokeratin and vimentin , metatstatic renal cell carcinoma was considered , although the tumor cells were negative for cd10 that is used as a marker for clear cell , renal cell carcinoma . the resected liver showed a solid mass measuring 7.56.53.7 cm and with a well - circumscribed border that was continuous with the glisson 's capsule and pushing the hepatic parenchyma . the mass was mostly solid , partly myxoid and hemorrhagic , and partly cystic with multiple , various sized cysts ( fig . 1f ) . the cut surface of the solid portion of the mass was mostly whitish - yellow , partly reddish , smooth , and glistening . microscopically , the tumor showed proliferation of flattened or cuboidal epithelioid cells in tubular or glandular structures as well as highly vascular stroma with thin - walled blood vessels ( fig . the epithelioid cells were diffusely positive for cytokeratin ( ae1/ae3 ) , vimentin , calretinin , and cytokeratin 5/6 , were focally positive for cd10 , and were negative for wt1 and cd34 ( fig . 3 ) . these findings support the mesothelial differentiation of the tumor cells . apart from this mass , there was an hepatic mass , measuring 2 cm in diameter and located in the right hepatic dome ; the mass was a typical , cavernous hemangioma ( fig . adenomatoid tumors of mesothelial derivation have been most often found in the male and female genital tracts , and are rarely reported in extragenital sites such as the adrenal gland , heart , mediastinum , appendix , intestinal mesentery , liver , pancreas , peritoneum , and pleura . only two cases of hepatic adenomatoid tumor have been described in the medical literature , one of which was a solitary liver mass,6 and the other involving the liver and peritoneum.7 here , we report the first case of a large sized hepatic adenomatoid tumor combined with a hepatic hemangioma . in the preoperative liver core biopsy , two components were noted , i.e. cd34-positive thin blood vessels and cytokeratin positive cells . cd10 was focally positive at postoperative biopsy while it was negative at preoperative biopsy specimen that was insufficient for thorough pathologic examination . as the tumor cell was initially considered to be epithelial cells with cd10 immunopositivity , renal cell carcinoma was considered in the differential diagnosis , although the left renal cyst looked a simple benign cyst . retrospectively , as mesothelial cells are also positive for various epithelial markers , specific markers of mesothelial cells , including calretinin and wt1 , must have been examined in the liver biopsy specimen . the preoperative differential diagnoses included sclerosing hemangioma , inflammatory pseudotumor , slow - growing well - differentiated hepatocellular carcinoma , and metastastic renal cell carcinoma due to the hypervascular feature of the tumors . radiologically , the findings of adenomatoid tumors range from a solid tumor to a cystic tumor depending on the content of the cystic spaces , smooth muscle , and fibrous tissue.8 as these tumors are difficult to differentiate from other benign or malignant tumors on clinical examination , ultrasonography , ct , and mr imaging , the situation usually leads to obtaining a both histopathologic and immunohistochemical diagnosis . in general , the resected tumor in this patient was likely to be embedded in the liver parenchyma , abutted to the diaphragm , and pushing the normal structure oppressed but without infiltration or destruction . histologically , adenomatoid tumor is classified into four types ; adenoid or tubular ; angiomatoid or canalicular ; solid or plexiform ; and cystic.9 thread - like bridging strands crossing the pseudotubular spaces are the characteristic morphologic features of adenomatoid tumor10 which is usually composed of gland - like spaces lined by single cubodial cells with prominent nuclei . as the tumor cells are extremely flat , the possibility of adenocarcinoma such as epithelial bile duct cancer seems unlikely . also differential diagnoses of hepatic tumors composed of clear cell type include hepatocelluar carcinoma , metastatic clear cell carcinoma , and metastatic adrenal cortical carcinoma . and it is necessary to exclude vascular neoplasms such as hemangioma , epithelioid hemangioendothelioma , and lymphangioma . metastatic adenocarcinoma can be easily differentiated from adenomatoid tumor by its cytologic morphology such as an atypical and infiltrative border , the negativity for calretinin and ck5/6 , and the positivity for carcinoembryonic antigen and moc 31 . and differentiation from clear cell type tumors and vascular neoplasms can be made possible by the use of immunohistochemical stainings for blood vessel endothelial markers ( cd31 , cd34 , and factor viii ) , lymphatic vessel markers ( hbme-1 ) , cytokeratin and vimentin.11 in the present case , the enlarged and proliferating capillaries in the edematous stroma were positive for cd34 , while intervening epithelioid cells were negative for endothelial markers . another differential diagnosis of adenomatoid tumor includes lipoma and metastatic carcinomas.12 as in the present case , metastatic clear - cell renal - cell carcinoma has the most difficult differential diagnosis because renal cell carcinoma only expresses both positive for cytokeratin and vimentin and has clear tumor cells with various cellular atypia . in conclusion , preoperative core biopsy is important for obtaining a definite diagnosis in cases of large adenomatoid tumor arising in unusual sites in order to determine the optimal treatment because many adenomatoid tumors are small and incidentally identified . when the biopsy specimen reveals benign epithelioid cells , immunohistochemistry for mesothelial markers must be performed in addition to obtaining both epithelial and mesenchymal markers for an accurate differential diagnosis .
a 45-year - old male with alleged asymptomatic hepatic hemangioma of 4 years duration had right upper - quadrant pain and was referred to a tertiary hospital . computed tomography and magnetic resonance imaging scans revealed a hypervascular mass of about 7 cm containing intratumoral multilobulated cysts . 
 a preoperative liver biopsy was performed , but this failed to provide a definitive diagnosis . 
 the patient underwent a partial hepatectomy of segments iv and viii . 
 the histologic findings revealed multifocal proliferation of flattened or cuboidal epithelioid cells and a highly vascular edematous stroma . 
 immunohistochemistry findings demonstrated that the epithelioid tumor cells were positive for cytokeratin ( ae1/ae3 ) , vimentin , calretinin , and cytokeratin 5/6 , and were focally positive for cd10 , and negative for wt1 and cd34 , all of which support their mesothelial origin . 
 immunohistochemistry for a mesothelial marker should be performed for determining the presence of an adenomatoid tumor when benign epithelioid cells are seen .