osseous hemangioma is a benign vascular tumor and most frequently involves the bones of the axial skeleton ( 1 , 2 ) . osseous hemangiomas in the peripheral , tubular and flat bones are uncommon , and very few reports have described the radiologic findings of the osseous hemangioma of the ilium ( 1 - 3 ) .
osseous hemangiomas may have a wide variety of radiologic appearances , and the lesions occurred in the tubular or flat bones can be demonstrated as aggressive tumors showing cortical destruction with extraosseous mass formation and osteolytic lesions mimicking a malignant bone tumor ( 1 - 6 ) . on 2-fluoro [ fluorine-18]-2-deoxy - d - glucose ( f - fdg ) positron emission tomography ( pet ) ,
hemangioma has been classified as a metabolically stable tumor with low f - fdg uptake , but a recently reported case of hemangioma of the tibia showed high f - fdg uptake on pet / ct ( 7 ) .
we present a case of a cavernous hemangioma of the ilium mimicking an aggressive malignant bone tumor , which demonstrated a large osteolytic lesion with cortical destruction , extraosseous soft tissue mass formation , and irregular calcifications on ct and mr .
in addition , we describe the f - fdg pet / ct findings of the osseous hemangioma of the ilium , which showed heterogeneous f - fdg uptake .
a 22-year - old female presented with a gradually increasing pelvic mass with tenderness for 1 month .
there was no evidence of previous trauma or fever , and also there was no history of other medical or surgical disease and no evidence of pregnancy . on the physical examination , there was a palpable mass with tenderness in her left pelvic area .
a plain radiograph of the pelvis showed a huge , geographic osteolytic lesion with a thick and irregular sclerotic rim in the left ilium ( fig .
ct showed an ill marginated , 13  10 cm , osteolytic lesion of the left ilium with extraosseous soft tissue mass formation and intralesional stippled calcifications . on the contrast - enhanced ct
, the mass showed irregular , rim enhancement and focal enhanced soft tissue components ( fig .
the lesion had a heterogeneous intermediate signal on the t1-weighted images , a heterogeneous high signal on fat suppressed t2-weighted images , and irregular low signal septa on t1 and t2-weighted images .
after enhancement with gadolinium , the mass was demonstrated as a heterogeneously enhanced mass , as well as non - enhanced soft tissue components and septal structures ( fig .
1 g ) . after fasting for 6 hours , intravenous injection of 375 mbq of f - fdg was performed ( at that time , her blood glucose level was 92 mg / dl ) .
the pet scan ( 3 min / bed , 6 - 8 beds ) was obtained from 60 minutes post f - fdg injection .
f - fdg pet / ct scanning was done by discovery pet / ct scanner ( ge healthcare , milwaukee , wi , usa ) , and scans were acquired in 3d mode .
reconstruction was done by ordered subset expectation maximization ( osem ) ( 128  128 matrix , 3.27 mm slice thickness , subsets : 21 , iteration : 2 , post - filter : 5.14 fwhm ( mm ) , loop - filter : 4.69 fwhm , diameter : 60 cm ) after attenuation correction .
f - fdg pet / ct demonstrated heterogeneous f - fdg uptakes , which had low and high f - fdg uptake ( maximum standard uptake value [ suvmax ] = 5.1 ) within the mass ( fig . 1h - j ) . based on the imaging features , chondrogenic malignant bone tumor in the ilium was considered even though , when taking her age into account , it was unusual .
on gross examination , the mass appeared as a vascular mass containing central necrosis , irregular bony septa , and fibrous tissues .
histopathologic examination of the excised mass showed bony trabeculae with dilated vascular spaces filled with blood and endothelial lining ( fig .
1k ) , and it was confirmed as cavernous hemangioma of the ilium by the experienced musculoskeletal pathologists .
intraosseoous hemangiomas are benign hamartomatous vascular tumors of the bones , and they frequently involve the skull and vertebral column ( 1 - 3 ) .
the peripheral , long , tubular and flat bones are the least affected sites , and among them , the tibia and femur are the most common sites ( 1 ) .
very few cases of hemangioma affecting the pelvic bones have been reported ( 1 - 3 ) .
hemangiomas involving the vertebrae or skull are usually asymptomatic and they are often found incidentally on routine imaging studies .
however , hemangiomas in the peripheral and pelvic bones are usually symptomatically associated with pain , soft tissue swelling and pathologic fracture ( 1 , 2 , 5 ) .
our patient complained of tenderness with a palpable mass in her pelvis for a duration of approximately one - month .
intraosseous hemangiomas may have various radiologic findings . due to the diversity of radiologic features of this disease , a correct preoperative diagnosis is rarely made .
on plain radiographs , osseous hemangiomas may show a loculated , sunburst , moth - eaten , and soap bubble appearance due to engorged vessels and thickened trabeculae , and they rarely manifest expansile osteolytic changes ( 1 - 8 ) .
on ct , hemangiomas in the skull and spine can present a typical polka - dot or honeycomb appearance ; however ct findings of the hemangiomas in long and flat bones are non - specific and it is difficult to take into consideration osseous hemangiomas in a differential diagnosis
. they can be demonstrated as expanded lytic areas surrounded by coarse trabecular bone with or without a soft tissue component , a lesion with a " polka - dot " pattern , an osteoplastic lesion with a sun - burst - like pattern , honeycombed appearance with cortical defects , an irregular destructive lesion with scalloping on the inner surface of the sclerotic cortical bone , and occasionally calcifications have been reported ( 1 - 4 , 6 , 8 , 9 ) . in our case , the mass was depicted as an osteolytic lesion with cortical destruction and extraosseous soft tissue mass formation , stippled calcifications on ct , and enhanced , exophytic soft tissue components on contrast - enhanced ct mimicking chondrogenic malignant bone tumors . on mr ,
osseous hemangiomas usually show a variety of signals from low to very high signal intensities on t1- and t2-weighted images within the lesion according to the internal components such as dilated vessels , hemorrhage , blood clots , fibrosis , bony trabeculations , fat , and smooth muscles ( 1 - 7 ) .
osseous hemangiomas can show variable degrees of enhancement related to internal contents , as we mentioned above , after contrast administration .
low signal septal structures within the lesion on t1 and t2-weighted images , and the appearance of a bunch of grapes on t2-weighted and gd - enhanced images were also reported ( 3 , 6 - 8 ) . in our case , non - enhanced , thick , irregular , septa like structures of low signal intensity within the mass were demonstrated on mr , and we retrospectively thought that this finding could be perceived as a soap - bubble appearance lesion that can be shown in the usual osseous hemangiomas .
f - fdg pet / ct is increasingly being used to obtain more information for differentiating benign and malignant tumors . even though , there are some false positive and false negative f - fdg uptakes in benign and malignant bone tumors , respectively ,
hemangioma has been known to be a metabolically stable benign lesion on pet . in vertebral hemangioma , it has been reported to demonstrate from ametabolic , cold vertebra to low f - fdg uptake on pet / ct images .
this finding can help to differentiate a hemangioma from a metastatic lesion in the case of a vertebral hemangioma depicted as a photopenic defect at the tc mdp bone scan , which need to be differentiated from osteolytic metastatic lesions in patients with a malignant disease .
( 12 ) have described the suvs for f - fdg in 16 hemangiomas as ranging from 0.73 to 1.67 , and tian et al .
( 13 ) have described the suvs for f - fdg in 4 hemangiomas as ranging from 1.6 to 2.3 . however , cha et al . ( 7 ) recently reported the case of an intra - osseous hemangioma of the tibia which showed increased f - fdg uptake ( suv = 3.9 ) on pet / ct .
( 7 ) , our case of the osseous hemangioma of the ilium showed heterogeneously increased f - fdg uptake ( suvmax = 5.1 ) on pet / ct .
( 15 ) had described that f - fdg pet may provide useful information to differentiate hemangioma from malignant soft tissue tumors owing to the tendency of low f - fdg uptake in soft tissue hemangiomas . however , contrary to soft tissue and vertebral hemangiomas , osseous hemangiomas in the peripheral and flat bones can show high f - fdg uptake on pet / ct as in our case and the case from cha et al .
, there was no radiologic report describing osseous hemangiomas of the ilium which demonstrated an increased f - fdg uptake on pet / ct .
intraosseous hemangiomas of the long bones and ribs can be rarely demonstrated as an aggressive lesion showing extraosseous growth with the disrupted bony cortex ( 1 - 4 , 8) .
the differential diagnosis for a hemangioma of long bones included a giant cell tumor , aneurysmal bone cyst , fibrous dysplasia , and plasmacytoma ( 1 , 5 ) . in the case of hemangiomas of the flat bones which show aggressive growth and osteolytic lesions ,
malignant bone tumors can be considered as a primary differential diagnosis ( 1 , 3 - 5 ) . in our case ,
chondrosarcoma was the primary differential diagnosis although the incidence of the chondrosarcoma is rare for her age . in conclusion
, cavernous hemangioma of the ilium can show cortical destruction , stippled calcifications , and an extraosseous soft tissue mass formation , which can give the false impression of a chondrosarcoma .
furthermore , osseous hemangiomas in the peripheral and flat bones can demonstrate high f - fdg uptake on pet / ct .
although osseous hemangioma of the ilium is rare , when a young patient presented with an osteolytic lesion with an extraosseous soft tissue mass , stippled calcifications and thick septa or coarse traculations , osseous hemangioma should be taken into consideration in the differential diagnosis .
 osseous hemangioma is a benign vascular tumor , and it usually occurs in the vertebrae and the skull . 
 however , hemangiomas of flat bones are rare , and there are very few reports that describe the radiologic findings of osseous hemangioma of the ilium . 
 we report a unique case of large cavernous hemangioma mimicking a chondrogenic malignant bone tumor originated from the ilium in a 22-year - old female . 
 the mass showed stippled calcifications , heterogeneous enhancement with thick septa and enhanced soft tissue components on ct and mr , and also this mass demonstrated heterogeneous 2-fluoro [ fluorine-18]-2-deoxy - d - glucose ( 18f - fdg ) uptake on 18f - fdg pet / ct . 
INTRODUCTION
CASE REPORT
DISCUSSION