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we discuss the detection of an unusual disseminated metastatic recurrence of an intracranial hemangiopericytoma 8 years after surgery on positron emission tomography ( pet)/computed tomography ( ct ) , its impact on clinical management and explore its possible role in the follow - up of these patients in the future .
a 21-year - old man presented in 2001 with headache , tinnitus , intermittent nausea and vomiting for 6 months .
magnetic resonance imaging ( mri ) revealed an infratentorial , lobulated extra - axial mass with a wide dural base , which showed an isointense signal on t1-weighted images , and heterogeneous signal on t2-weighted images with prominent flow voids ( fig .
1c ) was also noted on the ct scan . on the basis of imaging ,
a diagnosis of an atypical meningioma was suspected and the patient underwent a right retromastoid suboccipital craniotomy which revealed a grayish - white , lobulated , vascular tumor .
there was a well - defined cleavage plane between the tumor and the cerebellum which aided total excision of the lesion along with the dura and underlying bone .
figure 1axial t2-weighted ( a ) , contrast - enhanced t1-weighted and ct image in bone window through the posterior fossa .
( a ) a lobulated mass is seen showing a heterogeneous hyperintense signal on t2-weighted images with flow voids within ( arrow ) .
( b ) intense enhancement on postcontrast t1-weighted image with an associated dural tail ( arrow ) . ( c )
axial t2-weighted ( a ) , contrast - enhanced t1-weighted and ct image in bone window through the posterior fossa .
( a ) a lobulated mass is seen showing a heterogeneous hyperintense signal on t2-weighted images with flow voids within ( arrow ) .
( b ) intense enhancement on postcontrast t1-weighted image with an associated dural tail ( arrow ) . ( c )
he then received stereotactically confirmed external radiation therapy ( rt ) to a dose of 54  gy in 30 fractions over 41 days .
following completion of treatment he was asymptomatic and on regular follow - up for about 8 years , when in 2009 he presented with a firm , non - tender swelling on his back on the right side .
a biopsy of the swelling revealed a spindle cell tumor exhibiting a prominent hemangiopericytomatous pattern ( fig . 2a ) . on immunohistochemistry ( ihc ) , cd34 highlighted the stag horn vasculature with patchy positivity within the tumor ( fig .
in view of the soft tissue location of the tumor and its histopathological features ( including ihc profile ) , a differential diagnoses of a synovial sarcoma and a metastatic hemangioperictyoma were considered .
translocation studies were recommended for syt - ssx analysis by reverse transcriptase - polymerase chain reaction ( rt - pcr ) technique to discriminate between the two .
the negative results ruled out a synovial sarcoma and a final diagnosis of hpc was offered in the overall clinicopathological context . 

immunohistochemical results : ( b ) cd34 positivity in patchy areas of the tumor ; ( c ) mic2 positivity in tumor cells ; ( d ) tumor cells displaying bcl2 positivity ; ( e ) focal areas showing positive ema expression .
immunohistochemical results : ( b ) cd34 positivity in patchy areas of the tumor ; ( c ) mic2 positivity in tumor cells ; ( d ) tumor cells displaying bcl2 positivity ; ( e ) focal areas showing positive ema expression .
the patient then underwent a pet / ct study which revealed multiple asymptomatic osseous lesions with associated soft tissue masses involving the right - sided chest wall ( fig .
figure 3fusion pet / ct images show metastatic osseous lesions ( arrows ) with associated soft tissue masses in the right posterior chest wall ( a ) , right hemipelvis ( b ) and the left hemimandible ( c ) .
fusion pet / ct images show metastatic osseous lesions ( arrows ) with associated soft tissue masses in the right posterior chest wall ( a ) , right hemipelvis ( b ) and the left hemimandible ( c ) .
hpcs are rare tumors that arise from the zimmerman pericytes , cells surrounding the capillary and postcapillary venules .
those located in the central nervous system are rare and meningeal hpcs account for < 2.5 % of all meningeal tumors and < 1% of all intracranial tumors .
a slight male preponderance is reported , with most cases occurring in the middle - aged group . on imaging ,
most intracranial hpcs are supratentorial in distribution ; the commonest location is the parasaggital area .
hpcs appear predominantly isointense on t1- and t2-weighted images and show marked contrast enhancement on ct and mri .
unlike meningiomas , hpcs do not show calcification or associated hyperostosis of the underlying bone . on the contrary hpcs
these features help in radiological differentiation of the two entities , which otherwise occur at similar intracranial sites .
histopathologically hpc shows a stag horn vascular pattern of spindly cells . at times , the histopathologic features of a hpc and meningioma can overlap .
classically , while hpc shows positivity for cd 34 , a meningioma is ema positive .
the cornerstone of treatment in patients with meningeal hpcs is complete resection of the tumor with the underlying dura and bone .
addition of postoperative radiotherapy is the norm and has shown a significant reduction in rate of local recurrence when compared with surgery alone .
however , hpcs are inherently aggressive and tend to recur locally and distally , with extraneural metastatic recurrence reported in as many as 23% of cases ; the commonest sites are the lungs and the bones . radical surgical treatment of metastasis has shown improved survival and is being increasingly used in patients with metastatic disease .
this brings into focus the role played by imaging in excluding other metastatic sites prior to surgery for seemingly isolated metastasis . in the setting of recurrent disease , locoregional imaging of the clinically suspected site
thus , the onus of exclusion or confirmation of recurrence has so far been with conventional locoregional imaging modalities .
our patient presented with a solitary swelling in the back , which in fact was only a part of disseminated metastatic disease uncovered by whole body pet / ct imaging .
this precluded a possible resection of the chest wall tumor and put the patient on palliative therapy .
presented a report of an intracranial hpc with extracranial metastases and reviewed 19 cases from the available literature .
similar findings have also been described by others , in which the patients had multiple sites of metastases separated from each other in time and anatomic location .
in addition , in lieu of asymptomatic metastases as seen in our case , it is a reasonable step to subject patients treated for hpc to whole body imaging modalities like pet / ct to assess feasibility or futility of radical surgery .
our case thus highlights the role of pet / ct in uncovering the multiplicity of metastatic recurrence even in tumors like hpc , which are not routinely imaged with pet .
a few isolated reports have described the pet / ct findings of hpc at initial presentation ; however , its value in the setting of recurrence and restaging as described in our report has not been studied hitherto .
whether or not pet / ct can make an impact on deciding the management of patients with recurrent hpcs as described in our case remains to be seen and certainly merits validation with larger prospective studies .
abstractintracranial meningeal hemangiopericytomas are rare tumors that can mimic meningioma on imaging and on histopathology . however , these tumors are more aggressive with a tendency for local and metastatic recurrence , sometimes after a prolonged symptom - free interval . 
 we report an unusual metastatic recurrence of an intracranial hemangiopericytoma , 8 years after surgery for the primary tumor and discuss the role of positron emission tomography / computed tomography in the follow - up of these patients .