giant cell tumor ( gct ) of bone usually occurs in the epiphyses of long bones like the distal femur , proximal tibia , distal radius and proximal humerus1 .
craniofacial bone involvement is rare but has been reported to occur in the mandible , temporal bone , maxilla , occipital and sphenoid23 .
the incidence of gct varies between regions and is highest amongst the asian population , especially the chinese and japanese where they account for nearly 15% of all primary bone tumors4 .
although generally thought to be benign tumors , gcts are known to be locally aggressive at times , with local recurrence occurring in about 25%-35% of patients3 .
this is a case of a 22-year - old female who was previously well till she experienced swelling and pain over her right temporal region for 18 months .
she had episodes of jaw locking and could hear clicking sounds when chewing or talking .
she sought medical help but was treated as temporomandibular disorder ( tmd ) and was given analgesics , physiotherapy and an occlusal splint . the pain reduced after the prescribed treatment and
the swelling was inconspicuous initially but increased in size and hence further investigations were carried out .
examination revealed a 22 cm swelling over the right temporal region which was firm and tender on palpation . upon opening her mouth ,
computed tomography ( ct ) scan showed an aggressive erosive tumor of the squamous temporal bone extending to the right temporomandibular joint ( tmj).(fig .
a magnetic resonance imaging ( mri ) of the brain and tmj was performed which showed an extra - axial mass at the right middle cranial fossa involving the right tmj , measuring 4.21.62.6 cm .
2 ) during surgery , we used a modified frontotemporal flap for access to the temporal bone and tmj . an intraoral right sulcular incision along the ascending ramus of the mandible was used for access to the coronoid process .
intraoperatively , the tumor was seen to invade the temporal bone , mandibular condyle , tmj and overlying temporalis muscle but did not invade the temporal dura .
the patient underwent right partial temporal craniectomy , removal of part of the mandibular condyle and zygomatic arch , excision of the coronoid process , and excision of the tmj.(fig .
histopathological examination of the tumor revealed fibrous connective tissue with a few foci of numerous multinucleated giant cells , histiocytes , neutrophils , lymphocytes and occasional foam cells .
gcts are usually benign but have been known to be locally aggressive and occasionally metastasize , especially to the lung789 . very rarely , gcts may turn into sarcoma4 .
the usual sites of occurrence are the epiphysis of long bones and less than 2% occur in the head and neck region where the usual sites are the sphenoid and temporal bones10 .
portions of the temporal bone form by endochondral ossification , which is the same way epiphyses of long bones are formed and thus it is possible that the temporal bone is more prone to develop gcts because of this11 .
patients usually present with progressive pain and swelling over the site . in the temporal region ,
hearing impairment and facial nerve paralysis can occur due to compression or local invasion from the tumor12 .
involvement of the tmj causes jaw locking , deviation of mandibular movement and clicking sounds .
we would like to highlight the danger of treating patients as tmd before a precise diagnosis is made .
a thorough history and examination should be done and a list of differential diagnoses should be considered , including tumors14 .
tmd may present with pain and swelling at the temporal area as in this case , but swelling in tmd is different and not common .
some patients may still have temporal swelling but the swelling should be softer on palpation and not persistent in size as compared to tumors .
the swelling seen in tmd may be present during and after chewing and should decrease gradually between meals .
gcts appear lytic , subarticular , eccentrically located and usually lack a sclerotic rim on radiographs .
ct will rarely provide information that helps physicians arrive at a diagnosis but may be useful in delineating tumor extent , evaluation of cortical integrity and determination of tumor recurrence15 . on mri ,
gcts have low signal intensity on t1-weighted images , heterogeneous high signal intensity on t2-weighted images and heterogeneous enhancement with gadolinium .
mri is the preferred imaging modality for gcts , as the diagnostic accuracy of mri is high and it can detect soft tissue and intra - articular extension16 .
macroscopically , most gcts are soft and fleshy and appear grey to light red or dark reddish - brown . there may be areas of cyst , hemorrhage or fibrous septa formation as well .
the margins are usually ill defined , which explains the high percentage of recurrence if only curettage is done417 .
gct is a neoplasm of stromal - like neoplastic cells that are able to recruit macrophage and multinucleate osteoclast - like giant cells .
histologically , gcts are characterized by the finding of large osteoclast - like multinucleated giant cells scattered among a background of plump or spindle shaped mononuclear stromal cells .
the stromal cells may be mitotically active but should not have abnormal or atypical mitotic cells .
these giant cells have approximately 10 - 20 nuclei per cell , but may have 100 or more nuclei
. there may be reactive bone formation usually at the periphery and reactive changes such as reactive fibrosis , necrosis , hemorrhage and xanthogranulomatous inflammation .
this is likely the reason the ultrasound - guided fine needle aspiration biopsy result showed a xanthogranuloma .
gcts often have abundance of neovascularization , which explains the hemorrhages that are frequently seen within such tumors418 .
it is important to consider lesions such as giant cell reparative granuloma , hyperparathyroidism , non - ossifying fibroma , chondroblastoma , solid areas of aneurysmal bone cyst , malignant fibrous histiocytoma and osteogenic sarcoma4 .
surgery with the aim of wide excision is the mainstay of treatment for gcts , preferably with a wide margin of normal tissue81619 .
radiotherapy is reserved for cases where wide excision can not be achieved or for patients who are not fit for surgery .
irradiation - induced sarcomatous transformation is a known risk with orthovoltage radiation , but interestingly there is less risk with current use of megavoltage radiation19 .
denosumab , a receptor activator of nuclear factor kappa - b ligand ( rankl ) inhibitor has been approved for use in recurrent and unresectable gcts20 .
high dose dexamethasone therapy had been used effectively to rapidly reduce the size of these tumors but unfortunately , discontinuation of steroids is associated with re - growth in nearly every case4 .
 giant cell tumor ( gct ) of the craniofacial bones has been reported but they are not common . 
 this tumor occurs more often in women than in men and predominantly affects patients around the third to fifth decade of life . 
 gcts are generally benign but can be locally aggressive as well . 
 we report a case of gct involving the temporomandibular joint ( tmj ) , which was initially thought to be temporomandibular disorder ( tmd ) . a 22-year - old female presented with swelling and pain over the right temporal region for 18 months associated with jaw locking and clicking sounds . on examination , 
 her jaw deviated to the right during opening and there was a 22 cm swelling over the right temporal region . despite routine treatment for tmd , the swelling increased in size . 
 computed tomography and magnetic resonance imaging of the brain and tmj revealed an erosive tumor of the temporal bone involving the tmj which was displacing the temporal lobe . 
 surgical excision was done and the tumor removed completely . 
 histopathological examination was consistent with a gct . 
 no clinical or radiological recurrence was detected 10 months post - surgery . 
I. Introduction
II. Case Report
III. Discussion