solitary fibrous tumor ( sft ) is a rare tumor which was first described as originating from the pleura and occurring most commonly in the thoracic cavity3,9,12 ) .
however , it is now recognized that these rare tumors can occur throughout the body7,14 ) .
there have been only 8 case reports of extradural spinal sft , also only 8 case reports of head and neck sft involving bony structures4,5 ) .
although the majority of sft are benign , sometimes these tumors show aggressive clinical course including recurrence or multiple invasions , report on a malignant sft of the spine or skull is extremely rare5 ) .
we report on a first case of malignant sft of tandem lesions in the skull and spine with a rapid recurrence and metastasis .
a 54-year - old female patient was referred to our spine center with a two - month history of lower back pain and radiating pain in both legs , which was persistent even at night .
lumbo - sacral magnetic resonance imaging ( mri ) showed a heterogeneously enhanced 6.7 cm sized lesion involving the sacrum , sacroiliac joint , and both illium with extraosseous mass formation containing a necrotic portion ( fig . 1a ) .
we performed positron emission tomography / computed tomography ( pet / ct ) and bone scan to assess for metastatic lesion .
pet / ct and bone scan revealed hot uptake in the sacro - pelvic area , t8 , and occipital skull area .
thoracic mri showed an epidural enhancing 1.7 cm sized lesion in the posterior element of t8 ( fig .
in addition , findings on brain imaging studies showed an enhancing mass measuring 3.8 cm with occipital bone destruction and mild brain compression ( fig .
pathology of the biopsy indicated a type undetermined malignant neoplasm , suspected as a malignant spindle cell tumor . on angiography , large feeding vessels were observed in sacral lesion , and tumor embolization using gelfoam was performed prior to perform an open surgery .
partial removal of the tumor in sacroiliac area was done ; then , gross total removal of the tumor at t8 was subsequently performed in a single stage .
the tumor was extremely hypervascular and was not well demarcated . for the remnant tumor of the sacroiliac area , postoperative stereotactic radiosurgery using novalis tx ( brainlab , inc .
, ammerthalstrabe , germany ) was administered at a dose of 4 fractionated 32 gy , which encompassed 100% of the tumor volume .
after open surgery and radiosurgery , her lower back pain and radiating pain showed improvement .
three weeks after first open surgery , gross total removal of the tumor in the occipital skull was performed after tumor embolization .
tumors of the sacro - pelvic area , t8 , and occipital area showed identical histologic features .
the tumors consisted of fusiform or spindle cells and showed a hemangiopericytoma - like perivascular pattern or a so - called patternless pattern , with intervening irregular hyalinzed collagen bundles , typical for a solitary fibrous tumor .
mitotic figures were frequently observed [ up to 10/10 high - power fields ( hpfs ) ] . by immunohistochemistry ,
the tumor cells were positive for cd34 , cd99 , bcl-2 and ema ( focal - like + ) .
as a result , the tumors were diagnosed as malignant solitary fibrous tumor ( fig .
although there was a lack of clinical evidence about adjuvant chemotherapy or radiotherapy , adjuvant chemotherapy with adriamycin and cisplatin was administered .
however , just 2 days after starting adjuvant chemotherapy , one month after the initial surgery , she complained of aggravated upper back pain and paraparesis .
findings on follow - up thoracic mri showed a recurred expansive posterior epidural mass with cord compression at t8 ( fig .
follow - up whole spine mri and chest radiography revealed metastasis in multiple vertebrae and both lungs .
although palliative cervical and thoracic spine radiotherapy ( dose of 5 fractionated 15 gy ) was performed for relieving intractable pain , her symptoms did not show improvement and the patient finally died due to poor general condition six months after first open surgery .
classically , sft , also known as localized fibrous tumor , has been known as a rare spindle - cell neoplasm originating from the pleura . since the first case report in 1931 , studies of sft from the pleura were prolific in the 1980s12,15 ) .
although sft occurs mainly in the pleura , it can be seen in various organs , and has recently been considered to be a mesenchymal neoplasm originating from ubiquitous dendritic interstitial cells2 ) . according to previous studies , approximately 30% of sft arise in extrathoracic locations11 ) .
reported extrathoracic locations include the mediastinum , pericardium , peritoneum , retroperitoneal space , pelvis , adrenal gland , kidney , liver , periosteum , salivary gland , thyroid gland , lacrimal gland , breast , nasopharynx , orbit , urogenital system , skin , meninges , and spinal cord10 ) . due to overlapping histologic features , differentiation of sft from other soft tissue tumors may be difficult .
performance of immunohistochemical staining is necessary in order to rule out other differential diagnoses19 ) .
typical immunohistochemical features of sft are a positive result for cd34 , bcl-2 , and cd99 , and a negative result for -sma , desmin , pan - cytokeratin , and s-100 protein11 ) . however , these markers are frequently overexpressed in a range of other soft tissue tumors including hemangiopericytoma4 ) . as a result ,
a differential diagnosis of hemangiopericytoma with sft is difficult , even though their clinical courses are obviously different16 ) .
therefore , 2002 world health organization criteria for soft - tissue tumors treats those two neoplastic entities as a single section , and many lesions that were called hemangiopericytomas prior to 1990 could now be called sft5,10 ) .
however , in general , hemangiopericytomas are more cellular and have higher ki-67 rated of 5 - 10%6 ) . in the current case ,
most thoracic sfts are asymptomatic at presentation and are diagnosed as incidental finding on radiographs and ct images of the chest9 ) .
extrathoracic sfts , however , are usually symptomatic ; depending on location , the manifestations are a painless mass or local pressure effects . in addition , an association of approximately 5% of sfts with hypoglycemia due to secretion of insulin - like growth factors has been reported20 ) . in the current case , initially , the patient complained lower back pain with radiating pain in both legs due to compression of nerve roots of s1 and s2 . in imaging studies , including mri and ct , imaging features of sft are relatively nonspecific .
however , in general , sfts have discrete margins , and the majority of sfts have shown a lobulated contour .
sfts were typically well defined , tending to displace adjacent structures , and local invasion is not common .
however , in our case , the tumor margin was not well defined , and local invasion was obvious .
as in the current case , a useful distinguishing imaging feature of sfts is the presence of large collateral feeding vessels .
however , the presence of these vessels does not appear to be related to the histologic subtype of the tumor20 ) . on the other hand ,
the tumor occurred in multiple tandem regions , including the skull , thoracic spine , lumbo - sacral spine , and plevic bone .
the current report is first case about the malignant sft of multiple tandem lesions . at present , due to the rarity of the disease , standard therapies for malignant sft have not been well established .
surgical en bloc removal has been recommended as the treatment of choice for sft9 ) .
recurrence occurred commonly in cases involving incomplete excision , possibly caused by the level of difficulty in achievement complete resection . in these cases ,
the majority of sfts are benign , and the malignant form accounts for 9 - 22%6,11 ) .
based on previous case reports , malignant sft showed rapid local recurrence and distant metastasis6 ) .
some authors have suggested that the size of a sft is one of the best indicators of malignancy1,13,17 ) .
in addition , findings such as nuclear atypia , increased cellularity , necrosis , and greater than 4 mitoses/10 hpfs , are suggestive of the malignant potential of sfts18 ) .
otherwise , some studies have reported that the prognosis of an sft is most likely dependent upon complete resection rather than histologic findings8 ) .
hence , careful follow - up may be needed , even if the tumor is small and benign in appearance at the time of presentation5,8,11 ) .
the current patient showed malignant characteristics with respect to tumor size , multiple lesions , local invasion , impossibility of complete resection , and histopathologic findings .
fortunately , at initial presentation , the current patient showed a significant response to open surgery and radiosurgery . however , despite multidisciplinary treatment including adjuvant chemotherapy and radiotherapy , the tumor showed rapid local recurrence and aggressive metastasis to the whole spine and lung .
the authors report here the first case of patient with malignant sft of tandem lesions in the skull and spine with a rapid recurrence and metastasis .
although malignant sft is extremely rare , it should be considered in the differential diagnosis of tumors in the spine and skull , and carful follow - up is needed .
 a solitary fibrous tumor ( sft ) is a rare neoplasm originated from the pleura , but they can occur in a variety of extrathoracic regions . although many cases of primary sft have been reported , there are extremely rare repots to date of a malignant sft in the spine or skull . 
 a 54-year - woman visited our hospital due to low back pain and both leg radiating pain . 
 several imaging studies including magnetic resonance imaging and computed tomography revealed expansive enhanced lesions in the occipital bone , t8 , s1 - 2 , and ilium , with neural tissue compression . 
 we performed surgical resection of the tumor in each site , and postoperative radiosurgery and chemotherapy were performed . 
 however , after six months , tumors were recurred and metastasized in multiple regions including whole spine and lung . 
 the authors report here the first case of patient with malignant sft of tandem lesions in the various bony structures , including skull , thoracic spine , and sacral spine , with a rapid recurrence and metastasis . 
 although malignant sft is extremely rare , it should be considered in the differential diagnosis and carful follow - up is needed . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION