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cystic echinococcosis ( ce ) is the larval cystic stage of the tapeworm echinococcus granulosus ( 1 ) .
the disease is endemic in the central asia , mediterranean countries ; middle east , africa and south america ( 12 ) .
human become infected by accidentally ingesting of contaminated food and water with eggs of the tapeworm ( 1 , 3 ) . ingestion of eggs of the adult parasite results in the development of one or several unilocular hydatid cysts in humans , mainly in the liver ( 70% ) and lungs ( 20% ) . however , the larvae may pass through the liver and lung barriers and reach the other body sites .
the unusual locations of hydatid cyst in human are included , but not limited to , the heart , orbit , brain , spleen , muscle , salivary gland , bone , urinary tract , and pancreas ( 4 ) .
frequency of splenic hydatid cyst is low ( about 0.5 to 6% of total incidence of hydatid cyst ) even in endemic areas ( 4 , 2 ) .
splenic hydatid cyst is usually asymptomatic and symptoms are few and nonspecific and patients may be asymptomatic for 5 up to 20 years before the diagnosis ( 5 ) .
complications with splenic hydatid cyst are including , secondary infection , fistulization to adjacent tissues and cyst rapture to the peritoneal cavity , which in turn may cause a life - threatening systematic anaphylactic reaction .
diagnosis of splenic hydatid cyst is usually established during abdominal ultra - sound exam , performed for other clinical reasons .
based on mitochondrial dna ( mtdna ) analysis , the e. granulosus complex has been split into e. granulosus sensu stricto ( genotypes g1 , g2 and g3 ) , e. equinus ( g4 ) , e. ortleppi ( g5 ) and the still controversial taxon e. canadensis ( g6-g10 )  ( 6 ) . most of human cases are related to g1 strain of e. granulosus . here
a 41-yr - old woman admitted at department of surgery at shahid beheshti hospital in yasuj , southwest of iran .
abdominal sonography evaluation revealed a large cyst in the spleen , measuring 150 x 130 mm .
the cyst had a tick wall protruded from inferomedial aspect of spleen with patches of wall calcification .
low level of hemoglobin ( hb=10.7 grams per deciliter ) was noticed in her hematology tests .
splenectomy was performed for the patient and surgical interventions revealed a hydatid cyst occupying most of splenic parenchyma ( fig .
. gross picture of the spleen hydatid cyst ( original ) cut section of the splenic hydatid cyst with huge secondary infection ( original ) cut section of the splenic hydatid cyst showing calcified cyst layer ( original ) isolated sections of the cyst showing the cyst layers ( original ) she was discharged on 5th postoperative day .
postoperative diagnosis and confirmation of hydatid cyst was done by histopathological , molecular and serological approaches .
patient serum was evaluated by agb - elisa , as described before , and was found to be positive by this sensitive serological assay ( 7 ) .
the patient was housekeeper , used to have contact with animals including dogs and was from a known ce endemic area , where the hydatid cyst is quite common in both human and animals ( 2 ) .
for the purpose of molecular characterization , a few parts of the cyst were stored in 70% ethanol until use .
extraction was done using 15 l of proteinase k and 300 l of lysis buffer ( 50 ml of tris - hcl ( 100 mm ) , ph = 8 ; 1 mm of edta , ph= 8 ; 1% tween 20 ) followed by phenol / chloroform / ethanol / acetate extraction .
precipitated dna was re - suspended in 100 l of double - distilled water and stored at 20c until use .
pcr primer sets were used for amplifying a 280 bp fragment of mitochondrial 12s rrna gene of e. granulosus , using g1 forward : 5 gcttttgtgtggattatgcg-3 and g1 reverse : 5 tcaaaccagacatacaccaa- 3 primers ( 8) .
pcr reaction was carried out in a final volume of 25 l , containing 2 l of dna template , 0.5 l of each primer ( 10 pmol ) , 12.5 l of master mix and 9.5 l of double - distilled water .
pcr product was separated by electrophoresis in 1.5% agarose gel and stained with gel - red .
thermocycler was programmed by one cycle of initial denaturation at 94 c for 4min , followed by 35 cycle of denaturation at 94 c for 94 seconds , annealing at 57 c for 30 seconds , extension at 72 c for 35 seconds and final extension at 72 c for 4 min .
pcr product was excised from the 1.5% agarose gel and purified with a dna gel extraction kit , according to the manufacturer s instructions ( bioneer s accuprep gel purification kit ) .
pcr product was sequenced and the sequence of the isolate was aligned and compared with those of available sequences of e. granulosus in the genbank .
the sequence of the isolate showed the most identity with accessible sequences of echinococcus g1 genotypes , including eu275231.1 ( from sheep from iran ) , gq856696.1 ( from bovine from iran ) , gq913684.1 ( from goat from iran ) , kj801848.1 ( from sheep from argentina ) , kj801849.1 ( from human from yemen ) and ab979277.1 ( from human from japan ) ( fig 5 ) .
alignment of sequence of the 12s rrna gene of e. granulosus isolated from the patient with some 12s rrna gene of e. granulosus available in the genbank .
fahydatid - hu : sequence of the current splenic hydatid cyst ; eu275231.1 ( from sheep , iran ) ; gq856696.1 ( from bovine , iran ) ; gq913684.1 ( from goat , iran ) ; kj801848.1 ( from sheep , argentina ) ; kj801849.1 ( from human , yemen ) ; ab979277.1 ( from human , japan )
a 41-yr - old woman admitted at department of surgery at shahid beheshti hospital in yasuj , southwest of iran . she had been admitted because of abdominal pain .
abdominal sonography evaluation revealed a large cyst in the spleen , measuring 150 x 130 mm .
the cyst had a tick wall protruded from inferomedial aspect of spleen with patches of wall calcification .
low level of hemoglobin ( hb=10.7 grams per deciliter ) was noticed in her hematology tests .
splenectomy was performed for the patient and surgical interventions revealed a hydatid cyst occupying most of splenic parenchyma ( fig .
. gross picture of the spleen hydatid cyst ( original ) cut section of the splenic hydatid cyst with huge secondary infection ( original ) cut section of the splenic hydatid cyst showing calcified cyst layer ( original ) isolated sections of the cyst showing the cyst layers ( original ) she was discharged on 5th postoperative day .
postoperative diagnosis and confirmation of hydatid cyst was done by histopathological , molecular and serological approaches .
patient serum was evaluated by agb - elisa , as described before , and was found to be positive by this sensitive serological assay ( 7 ) .
the patient was housekeeper , used to have contact with animals including dogs and was from a known ce endemic area , where the hydatid cyst is quite common in both human and animals ( 2 ) .
for the purpose of molecular characterization , a few parts of the cyst were stored in 70% ethanol until use .
extraction was done using 15 l of proteinase k and 300 l of lysis buffer ( 50 ml of tris - hcl ( 100 mm ) , ph = 8 ; 1 mm of edta , ph= 8 ; 1% tween 20 ) followed by phenol / chloroform / ethanol / acetate extraction .
precipitated dna was re - suspended in 100 l of double - distilled water and stored at 20c until use .
pcr primer sets were used for amplifying a 280 bp fragment of mitochondrial 12s rrna gene of e. granulosus , using g1 forward : 5 gcttttgtgtggattatgcg-3 and g1 reverse : 5 tcaaaccagacatacaccaa- 3 primers ( 8) .
pcr reaction was carried out in a final volume of 25 l , containing 2 l of dna template , 0.5 l of each primer ( 10 pmol ) , 12.5 l of master mix and 9.5 l of double - distilled water .
pcr product was separated by electrophoresis in 1.5% agarose gel and stained with gel - red .
thermocycler was programmed by one cycle of initial denaturation at 94 c for 4min , followed by 35 cycle of denaturation at 94 c for 94 seconds , annealing at 57 c for 30 seconds , extension at 72 c for 35 seconds and final extension at 72 c for 4 min . after pcr amplification ,
pcr product was excised from the 1.5% agarose gel and purified with a dna gel extraction kit , according to the manufacturer s instructions ( bioneer s accuprep gel purification kit ) .
pcr product was sequenced and the sequence of the isolate was aligned and compared with those of available sequences of e. granulosus in the genbank .
the sequence of the isolate showed the most identity with accessible sequences of echinococcus g1 genotypes , including eu275231.1 ( from sheep from iran ) , gq856696.1 ( from bovine from iran ) , gq913684.1 ( from goat from iran ) , kj801848.1 ( from sheep from argentina ) , kj801849.1 ( from human from yemen ) and ab979277.1 ( from human from japan ) ( fig 5 ) .
alignment of sequence of the 12s rrna gene of e. granulosus isolated from the patient with some 12s rrna gene of e. granulosus available in the genbank .
fahydatid - hu : sequence of the current splenic hydatid cyst ; eu275231.1 ( from sheep , iran ) ; gq856696.1 ( from bovine , iran ) ; gq913684.1 ( from goat , iran ) ; kj801848.1 ( from sheep , argentina ) ; kj801849.1 ( from human , yemen ) ; ab979277.1 ( from human , japan )
hydatid disease is an endemic zoonosis in many parts of iran and is an important medical and veterinary concern in many countries .
the most common locations for hydatid disease are the liver and lungs , but any organ or tissue can potentially be affected by this disease ( 45 ) . primary splenic involvement in hydatid cyst is uncommon , as the parasite embryo usually trapped in the liver ( as first filter ) and the lung ( as second filter ) .
clinical presentation of hydatid disease depends on the size , site and depth of the cyst .
the most common symptoms are abdominal pain and palpable mass in the left upper quadrant .
moreover , rapture of spleen cyst may cause systemic anaphylactic reaction leading to dyspnea , pruritus , edema or even death .
the majority of splenic infestations are diagnosed following incidental findings at radiographic examination for unrelated complaints .
hydatid cyst is diagnosed mainly by history , imaging , and serological methods ( 914 ) .
the performance of serological tests in the diagnosis of splenic hydatid cyst might not be satisfactory . in a series of 6 cases of splenic hydatid cyst ,
only 3 cases ( concurrent cysts in spleen and liver ) were positive by the serological methods and the remaining 3 cases , which had only splenic hydatid cyst , were negative ( 15 ) . in two cases of splenic hydatid cyst in greece ,
, serological evaluation revealed anti - hydatid cyst antibodies in patient serum , using antigen - b elisa .
seropositivity of our case might be contributed to the use of a reliable serological test and the feature of the current splenic cyst , which was large and primary .
blood eosinophilia may present in less than 30% of patients with splenic hydatid cyst , make this blood parameter an unreliable laboratory finding .
for treatment of splenic hydatid cyst , splenectomy is preferred in adults and is required when the cyst is particularly large or centrally located ( 17 ) .
so far , ten different genotypes ( g1-g10 ) have been identified for e. granulosus sensu lato by molecular approaches ( 6 ) .
the g1 genotype or sheep strain of e. granulosus sensu stricto is the most common genotype of e. granulosus in animals and humans worldwide ( 6 , 1819 ) .
the predominant strain of e. granulosus in human cases of hydatid cyst in iran is e. granulosus sensu stricto ( 20 ) . in keeping with this ,
although rare , hydatid cyst should be considered in differential diagnosis of all cystic masses in the spleen in any ce - endemic areas .
spleen is an unusual location for hydatid cyst . here 
 we report a case of primary splenic hydatid cyst in a 41-yr - old iranian woman from yasuj , southwest of iran . 
 the patient had been admitted to shahid beheshti hospital because of abdominal pain . 
 abdominal sonography revealed a hypoechoic lesion of 150 x 130 mm in the spleen , suggestive of hydatid cyst . 
 splenectomy was performed for the patient and surgical interventions revealed a hydatid cyst occupying most of splenic parenchyma . 
 she was discharged on the 5 day of her operation . 
 postoperative diagnosis and confirmation of hydatid cyst was done by histopathological , molecular and serological approaches . 
 histopathological evaluation revealed the classical laminated layer of hydatid cyst . 
 dna was extracted from a part of cyst and pcr amplified . 
 sequencing and analysis of pcr product revealed that the isolate has the most similarity with g1 strain of echinococcus granulosus . 
 patient s serum was positive for igg anti - hydatid cyst antibodies , using antigen - b elisa .