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mesenchymal hamartoma is a pediatric tumor occurring uncommonly in patients older than 5 years and is rarely reported in adult population .
it usually presents as an abdominal mass or with symptoms of compression of adjacent organs . in certain cases ,
the cystic nature of the tumor is attributed to the cystic degeneration of myxomatous mesenchyme or cystic dilatation of malformed bile ducts .
routine hematoxylin and eosin staining and immunohistochemistry studies have revealed mesenchymal hamartoma to be composed of spindle cells ( positive for smooth muscle actin and vimentin ; negative for cd31 , cd34 and s-100 ) and bile ducts ( positive for cytokeratin-7 [ ck-7 ] and negative for ck-20 ) .
an 81-year - old , elderly male patient presented to our hospital with a history of abdominal discomfort and distension for 20 days .
his laboratory investigations , including complete blood count , prothrombin time , activated partial thromboplastin time , serum bilirubin , serum alpha - fetoprotein and viral markers serology were within the normal limits .
liver enzymes were slightly elevated ( aspartate aminotransferase [ serum glutamic oxaloacetic transaminase ] : 40 u / l [ n : 15 - 37 u / l ] , alanine aminotransferase [ serum glutamic - pyruvic transaminase ] : 70 u / l [ n : 30 - 65
u / l [ n : 50 - 136 u / l ] and gamma - glutamyl transferase : 105 u / l [ n : 5 - 85 u / l ] ) . on abdominal sonography , a large cystic lesion in the left lobe of liver with thinned out peripheral hepatic parenchyma and few well - defined small hepatic cysts in right lobe of liver were reported .
the computed tomography scan was suggestive of abscess in left lobe with perilesional edema ( approximately 21.8  12.3  18.6 cm ) and few small cysts in right lobe of liver . on the basis of signs and symptoms and radiological investigations , a provisional clinical diagnosis of liver abscess
per operatively , a large cystic space occupying lesion containing turbid fluid was seen replacing the whole left lobe and so the patient underwent resection of left lobe with drainage .
gross examination revealed a flap like wall of a cyst measuring 21  10 cm with wall thickness ranging from 0.5 to 1.5 cm .
appearance of inner surface was dirty grayish brown rough with multiple small protrusions varying in size from 0.3 to 1 cm in diameter [ figure 1 ] .
normal liver tissue of size 6  2  2 cm was also identifiable at periphery of the specimen .
gross picture of specimen of mesenchymal hamartoma on light microscopy , representative sections revealed mixture of hepatocytes arranged in clusters and fibromyxoid stroma .
ductular structures embedded in fibrous stroma along with adipose tissue , nerve bundles , and congested blood vessels were also seen [ figure 2 ] .
h and e stained microscopic section showing bile duct proliferation embedded in fibromyxoid stroma along with hepatocytes
it constitutes approximately 8% of all pediatric tumors and only a few cases have been reported in adults .
only 31 cases of adult mesenchymal hamartoma have been previously reported as individual case reports in the english literature .
of these , 23 ( 74% ) cases have been reported in females and only 8 ( 26% ) in males with an average age of 40 and 57 years , respectively . as per literature review
, there seems no predilection for a particular lobe involvement in the adult hepatic mesenchymal hamartoma .
it has been equally ( 38.7% ) reported in the right and left lobes of liver .
however , in 22.6% cases involvement of both lobes of liver was seen . in 16 cases ( 51.6% ) ,
gross appearance of mesenchymal hamartoma was cystic , in 9 ( 29% ) cases was solid and in 6 cases ( 19.4% ) was both solid and cystic .
our patient was an 81-year - old elderly male presented with abdominal discomfort . in this case ,
mesenchymal hamartoma in the left lobe of liver with cystic gross appearance has been reported .
currently , the pathogenesis of mesenchymal hamartoma is still under study , the hypothesis of its origin from synchronous abnormal mesodermal development has been postulated .
it gradually enlarges up to large sizes , some can spontaneously regress and few can undergo malignant transformation to undifferentiated ( embryonal ) sarcoma .
karyotype study of undifferentiated embryonal sarcoma has revealed chromosomal rearrangement in 19q13.4 , which is similar to that in mesenchymal hamartoma .
this can be the probable explanation for the fact that mesenchymal hamartoma is potentially a premalignant lesion and might be a precursor lesion to undifferentiated embryonal sarcoma .
mesenchymal hamartoma is a rare hepatic lesion in adults , usually presents as a cystic lesion and can be a premalignant lesion .
surgical excision is the main therapeutic modality and necessary to make final definitive histopathological diagnosis .
mesenchymal hamartoma is a benign hamartomatous lesion with unknown histogenesis . 
 it generally occurs in pediatric population and has been rarely reported in adults . 
 we report an unusual case of a cystic mesenchymal hamartoma of liver in an 81-year - old elderly male . 
 a provisional diagnosis of liver abscess was made and definitive histopathology confirmed the diagnosis . 
 this case has been reported because of its rarity .