hemangiopericytoma is a mesenchymal tumor that occurs most commonly in the soft tissues of the upper and lower extremities , pelvis , and retroperitoneal space and seldom in visceral organs ( 1 ) . due to its vascular origin
transarterial embolization is a procedure which can be performed prior to surgery of highly vascular tumors in order to avoid perioperative bleeding .
although there are a few reports ( 3 , 4 ) of preoperative embolization of hemangiopericytomas , to our knowledge , there has been no report to apply a preoperative embolization of a primary hemangiopericytoma of the rib .
a 62-yr - old man was admitted to our department with the complaints of progressive dyspnea , an aching chest pain on the right side , malaise and anorexia with weight loss on 4 december 2001 .
his medical history was noteworthy for diabetes mellitus type ii , a 10-pack year history of smoking , and a moderate history of alcohol . on physical examination ,
a chest roentgenogram on admission demonstrated a large , indistinct opacity on the peripheral region of the right lower zone associated with blunting of the right lateral costophrenic sulcus .
computed tomographic ( ct ) scans of thorax revealed a homogeneous mass expanding the right seventh rib and invading into the adjacent lung , and a right sided pleural effusion ( fig .
histopathologic examination of the pleural biopsy specimens were reported as chronic pleuritis . to clearly identify the mass , a ct - guided , core needle biopsy was performed .
the ultrasonography and ct of the abdominopelvic region , magnetic resonance imaging of both upper and lower extremities and ct of the cranium were reported as normal .
preoperative angiography showed hypervascularization of the tumor from the right 7th and 8th ( fig .
2 ) , and also from 9th intercostal arteries . we performed embolization with polyvinyl alcohol ( pva ) particles .
firstly , we embolized arterioles within the tumor for which we used pva , 250 m in size .
then , embolization of the feeding arteries of the tumor was done with pva , 750 - 1,000 m in size .
complete resection of the mass with 7th , 8th , and 9th rib with a surgical margin of 5 cm and a wedge resection of the adjacent lung was done .
macroscopic evaluation of the resected tumor revealed an encapsulated and lobulated mass located posteriorly to the 6th to 9th ribs .
microscopic evaluation of the tumor revealed a solid mesenchymal mass composed of indistinct fusiform to rounded cells arranged around slit - like and branching thin - walled vessels ( fig .
immunohistochemically tumor cells stained positively for vimentin and focally for cd-34 , and negatively for cytokeratin , smooth muscle actin , s-100 and cd-31 .
hemangiopericytomas , that are believed to be derived from the vascular pericyte , rarely originate from ribs , although they can be found in any region which contains pericytes ( 5 ) .
but , it may be asymptomatic and may be detected as an abnormal shadow on a chest radiography film ( 3 ) .
the radiographic appearance is that of a mass on the lateral chest wall ( 6 ) . rarely , it may reach a huge size occupying two thirds of one hemithorax ( 7 ) . in our case
, thorax ct revealed that a large indistinct opacity on the peripheral region of the right lower zone on chest radiography was a homogeneous mass expanding the right seventh rib .
microscopically the tumor consists of numerous vascular spaces of variable size and shape separated by aggegates of tightly packed oval to spindle - shaped cells with bland nuclei .
mitotic figures and nuclear atypia are variable in number and degree ( 6 ) . in our case ,
microscopic evaluation of the tumor revealed a solid mesencymal mass composed of indistinct fusiform to rounded cells arranged around slit - like and branching thin - walled vessels .
gomori silver impregnation method revealed a dense reticulin meshwork confirming the perivascular distribution of tumoral cells .
the results of immunohistochemical studies were consistent with the diagnosis ( 8) . because hemangiopericytomas are highly vascular tumours ,
because the choice of treatment for primary ones is surgery , and because some authors ( 3 , 5 ) reported massive bleeding during the operation of hemangiopericytomas , we performed transarterial embolization preoperatively in order to prevent or decrease perioperative bleeding ( 3 ) . and
then , the patient underwent a right thoracotomy during which there was no any significant bleeding . because the recurrence rate was reported as 50% ( 7 , 9 ) , long - term follow - up is necessary for the patient . in our case
finally , our case report has two important features : 1 ) primary hemangiopericytoma of the rib is an extremely rare tumor ; 2 ) preoperative embolization of a primary hemangiopericytoma of the rib have not been reported heretofore .
 primary hemangiopericytoma of the rib is extremely rare and only a few cases have been reported . a 62-yr - old man presented with an aching chest pain and dyspnea . 
 thoracic computed tomography revealed a homogenous mass expanding the right seventh rib . 
 a diagnosis of hemangiopericytoma was established by percutaneous needle biopsy . 
 preoperative embolization of the feeding vessels of the tumor was performed in order to prevent perioperative bleeding . 
 there was no significant bleeding during the surgery , where complete resection of the tumor with 7th to 9th ribs with a surgical margin of 5 cm was performed . 
 postoperative course was uneventful and there has been no recurrence for thirteen months . to our knowledge , there has been no report to apply a preoperative embolization of a primary hemangiopericytoma of the rib . 
INTRODUCTION
CASE REPORT
DISCUSSION