document: chondroblastoma is a rare osseous tumor which accounts for less than 1% of all primary bone tumors , and affects the epiphyseal regions of the tubular bones , especially the ends of tibia , femur , and humerus . 
   chondroblastoma localized in the head and neck region is uncommon but characteristically occurs in the temporal bone or the temporomandibular joint ( tmj ) and results in various symptoms such as occlusal abnormalities , trismus , clicking of the tmj , hearing impairments , dizziness , and otorrhea . 
   malignant changes in chondroblastoma , although rare , have been observed after irradiation [ 3 , 4 ] . in order to avoid the inherent risk of malignant progression , radiation therapy should not be considered . 
   however , chondroblastoma in the temporal bone has unusual histological features that make diagnosis difficult , and incomplete resection carries a high risk of recurrence [ 5 , 6 ] . 
   thus , it would seem advisable , provided the diagnosis is accurate , to attempt a complete surgical removal for the curative treatment of chondroblastoma . following 5 years of unsuccessful treatment , 
   the patient was referred to our department presenting with chronic hearing impairments and subsequently progressive trismus . 
   a tumor mass was present in the middle cranial fossa , including the tmj and cochlea , in spite of earlier treatment regimens . by reporting this initially misdiagnosed case 
   an accurate diagnosis was delayed because the original diagnosis relied on imaging analysis with neither careful magnetic resonance imaging ( mri)/computed tomography ( ct ) scanning analysis nor histopathologic examination . 
   this less than thorough approach led not only to a delay of an accurate diagnosis and to unnecessary treatments , but also to a delay of suitable treatments for this rare chondroblastoma with malignant potential . 
   this study presents methods which are helpful in diagnosing chondroblastoma , as well as suitable surgical procedures for maintaining postoperative functionality . 
   a 41-year - old male with tmj disorder , initially diagnosed with otitis media , presented with a history of chronic ( lasting more than 1 year ) hearing loss on the right side . 
   the patient underwent several attempts at antibiotic therapy and treatment for eustachian tube blockage , but his symptoms were unresponsive to both systemic antibiotic agents and tubing therapy . 
   his initial diagnosis of tmj disorder was based on physical assessment of malocclusion and complaints of subsequently developed trismus . 
   after these 2 years , endoscopic surgery , followed by several attempts to correct the malocclusion for the tmj disorder , was implemented but resulted in no significant improvement in clinical manifestations . 
   the patient was further assessed and a ct scan and pathologic examination showed the presence of a giant cell tumor in the temporal bone . 
   the patient harbored the primary disease and consulted us for persistent restriction of the mouth opening as well as hearing loss and dizziness , which he had noticed 5 years earlier . 
   re - examination of the ct scan revealed that the tumor mass had progressively enlarged and had widely destroyed the middle cranial fossa in the temporal lobe ( fig . 
   1 ) . mri displayed the presence of a poorly defined mass , with predominantly low signal and relatively high signal intensities , on t1- and t2-weighted sequences , respectively , involving the right middle cranial fossa and infratemporal fossa floor . 
   the tumor mass invaded the right temporal lobe and destroyed the subzygomatic fossa ( fig . 
   hearing loss in the right ear , trismus , and paralysis in v2 had not been reported by the patient before visiting our department . 
   no paralysis was observed in v1 and v3 , nor in the facial , glossopharyngeal , or hypoglossal nerves . 
   re - examination of combined mri / ct scanning indicated rapid enlargement and widespread invasion of the mass into the cranial bone , with enlarged lymph nodes in the cervical region , providing evidence for chondrosarcoma or chondroblastoma in the temporal bone ( data not shown ) . 
   preoperative histopathologic studies of the biopsy specimens for s-100 protein ( rabbit polyclonal antibody ; dako , denmark ) were performed on formalin - fixed , paraffin - embedded tissues , using an avidin - biotin - complex method as instructed by the manufacturer . 
   histopathologic findings showed extensive proliferation of multinucleated giant cells with circular nuclei showing a sheet - like structure , formation of a small quantity of acidophilic substrate in the tumor mass , large cystic areas , and the presence of hemorrhage and aneurismal bone cysts indicating secondary aneurism - like bone cyst formation ( fig . 
   preoperative re - examinations of combined mri / ct scanning and pathologic findings revealed the features of chondroblastoma . 
   a generous c - shaped postauricular incision was made through the skin and subcutaneous tissue , which was elevated to expose the underlying fascia , periosteum , and muscle . 
   the incision was extended down to the cervical region to allow exposure of the sternocleidomastoid ( scm ) muscle , the carotid artery , and the internal jugular vein . 
   neck dissection was performed ranging in scope from removal of level ii and iii nodes to possible radical neck dissection , and total parotidectomy was performed while leaving facial nerves intact ( fig . 
   a radical mastoidectomy was performed to achieve complete exposure of the mastoid and tympanic segments of the facial nerve . 
   subtotal resection of the temporal bone and skull base dissection with resection of tmj using a zygomatic - extended middle fossa approach was carried out . 
   the temporal lobe dura was resected about 30 cm together with part of the temporal lobe . 
   the dura was reconstructed using fascia lata and covered with the pericranial flap and the temporalis muscle , and reconstruction using the scm and the platysma muscle was performed to prevent infection and dysfunction ( fig . 
   reconstruction of the facial tissue allowed the patient to open his mouth to the extent of 40 mm with no pain ( fig . 
   this study underlines an attempt to use conventional surgical procedures , with some modifications , for the treatment of chondroblastoma in order to prevent postoperative tmj dysfunction , including malocclusion , trismus , and dysphagia , while preserving the masseter , the coronoid process , and the anterior part of the temporal muscle . 
   reconstruction for facial tissues was carried out by inserting the scm muscle flap into the infratemporal fossa . 
   the scm flap was then fixed to the resected end of the zygoma inside the mandible . 
   four and a half years after surgery , enhanced ct imaging showed no residual tumor . 
   the patient had no clinical evidence of tumor recurrence during this period , nor of dizziness , with improvement of the occlusal abnormalities and trismus , indicating no postoperative dysfunction . 
   the patient did not undergo postoperative irradiation since this is contraindicated with a diagnosis of chondroblastoma . 
   the present study underlines the importance of an accurate diagnosis especially for a mass in the temporal bone . 
   tumors such as chondroblastoma , which may originate as benign , may become malignant under inappropriate treatment . 
   in fact , a combined radiotherapeutic - surgical approach may provoke neoplastic transformation in the residual tumor tissues of chondroblastoma [ 4 , 5 , 7 ] . following an inaccurate diagnosis , 
   the misdiagnosis was attributable to the difficulty of a differential diagnosis since the clinical manifestations can be indistinguishable from giant cell tumor , chondrosarcoma , aneurismal bone cyst , enchondroma , or chondromyxoid fibroma . immediately 
   before being referred to our department , the patient was misdiagnosed with giant cell tumor in the temporal region on the basis of ct scan / mri plus pathology . 
   re - examination of ct / mri indicated rapid enlargement and widely - spread invasion of a mass into the cranial bone , along with enlarged lymph nodes in the cervical region , showing a possibility of chondrosarcoma in the temporal bone . 
   however , the widely- and rapidly - enlarged mass was found to have infiltrated the temporal lobes , and to have destroyed the middle cranial fossa . 
   these findings provided evidence of malignant chondroblastoma in the temporal bone . the subsequent immunohistochemical examination of the lesion showed reactivity of the neoplastic protein mass for s-100 protein . 
   the presence of s-100 protein in tumor cells differentiates chondroblastoma from giant cell tumor , chondrosarcoma , and aneurismal bone cysts , favoring the diagnosis of chondroblastoma [ 8 , 9 , 10 ] . 
   the presence of associated aneurismal bone cysts is , while not absolute , a supplemental criteria for the diagnosis of chondroblastoma . these findings strongly suggest potentially malignant chondroblastoma . 
   treatment of a chondroblastoma in the temporal bone requires total en bloc excision , curettage , and irradiation . 
   postoperative irradiation has been performed with the intention to reduce the risk of postoperative recurrence . 
   however , it is not universally recommended due to malignant changes in chondroblastoma observed after irradiation . 
   , a total en bloc excision should be the first choice as a therapeutic approach for chondroblastoma in the temporal bone . in the case presented here , the tumor was located in a site that included important neurovascular components , which generally makes surgical resection impractical . 
   thus , accurate , early - stage diagnosis is a vital component to successful treatment . 
   for patients with later - stage chondroblastoma , our modified surgical procedure is a valuable alternative . 
   
summary: we present a case involving a late diagnosis of chondroblastoma of the temporal skull base involving the temporomandibular joint ( tmj ) . following an initial misdiagnosis and unsuccessful treatment over a period of 5 years 
   , the patient was referred to our department for further evaluation and possible surgical intervention for occlusal abnormalities , trismus , clicking of the tmj , and hearing impairment . based on preoperative immunochemical studies showing positive reaction of multinucleated giant cells for s-100 protein , 
   the final diagnosis was chondroblastoma . the surgical approach 
   postauricular incision and total parotidectomy , with complete removal of the temporal bone , including the tmj via the extended middle fossa  was successful in preserving facial nerves and diminishing clinical manifestations . 
   this study highlights a misdiagnosed case in an effort to underline the importance of medical examinations and accurate differential diagnosis in cases involving any tumor mass in the temporal bone .