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clear cell odontogenic carcinoma ( ccoc ) is an extremely uncommon tumor of odontogenic origin , first described by hansen in 1985 .
ccocs were formerly called clear cell ameloblastomas or clear cell odontogenic tumors and were classified under the category of benign tumors in the 1992 world health organization classification . however , owing to its high potential for regional spread and distant metastases , it was reclassified as a malignant tumor of odontogenic origin in 2005 . to date , of the reported cases , all have presented in a single jaw , with none having tmj involvement .
we report , to the best of our knowledge , the first case of an aggressive ccoc involving the mandible and the temporomandibuar joint ( tmj ) with cervical lymph node metastasis at presentation .
a 50-year - old female was referred our institution for evaluation of a swelling in the left mandible of 3 months duration .
she gave a history of extraction of a mobile left lower third molar one month ago elsewhere .
, there was an extra oral swelling overlying the left posterior mandible measuring 4  5 cm .
intraorally , the swelling extended from the region of the left first molar to the ascending ramus of the mandible , obliterating the left retromolar trigone .
the patient was also found to have grade 1 trismus and numbness of the left tongue .
examination of the neck revealed a significant , firm , submandibular lymph node approximately 1.0 cm in diameter .
orthopantomogram and computed tomography scans revealed an expansile lytic lesion involving the posterior body and ramus of the left mandible [ figure 1 ] .
there was perforation of both the buccal and lingual cortical plates and involvement of the adjacent soft tissues .
an intraoral trucut biopsy was performed , and a diagnosis of ccoc was established . a chest skiagram and ultrasound of the abdomen , done as a part of the metastatic work - up ,
( a ) opg showing a radiolucent lesion in the posterior segment of the left hemi - mandible .
( b ) reconstructed axial ct scan showing the lytic lesion along the left angle and ascending ramus of the mandible and involvement of the temporomandibular joint the patient then underwent a composite resection which included an en bloc excision of the posterior segment of the left mandible , tmj , infratemporal fossa clearance , and a left modified radical neck dissection [ figure 2 ] .
( a ) inraoperative clinical photograph following composite resection ( b ) postoperative clinical photograph of the operated specimen the gross pathology revealed a firm tumor measuring 5  3  4.5 cm involving the mandible , tmj , and the adjoining soft tissues .
microscopically , tumor cells were seen arranged in sheets , cords and islands , separated by thin and thick bands of fibrocollagenous stroma with hyalinization .
the tumor cells were round to polygonal with well - defined cell outlines and abundant clear cytoplasm .
the tumor cells were immunoreactive for keratin , epithelial membrane antigen , smooth muscle actin , and s-100 and negative for vimentin , and hmb-45 [ figures 3 and 4 ] .
h and e x10  ( a ) the tumor cells were round to polygonal with well - defined cell outlines and abundant clear cytoplasm .
( b ) tumor showing infiltration of the mandible . ( c ) tumor cell infiltrating the temporomandibular joint . ( d )
metastatic tumor deposits in the cervical lymph nodes ihc x100  ( a ) tumor cells showing strong immunopositivity to keratin .
( b ) tumor cells showing weak immunopositivity to ema . ( c ) tumor cells showing weak immunopositivity to sma .
( d ) tumor cells showing mild - to - moderate immunopositivity to s-100 adjuvant external beam radiotherapy was advised in view of the large erosive tumor with perineural infiltration and the presence of cervical lymph node metastasis .
the patient subsequently received 40 grey of external beam radiotherapy to the tumor bed and neck .
insight into the behavior of this tumor is based on a limited number of case reports .
the peak incidence is reported to occur in the fifth to seventh decades of life with a female preponderance .
( 1.62 : 1 ) the mean age at presentation was 54.45 years ( range 1789 years ) .
the most common presenting sign was as a painless swelling of the jaw , often with mobility of the teeth in that region .
palpable lymph nodes on initial presentation were noted in about 10% of the reported cases .
the etiology of this neoplasm remains poorly understood and the diagnosis of ccoc depends on the exclusion of other clear cell tumors .
the biphasic pattern is the most common , in which clear cell nests are intermixed with polygonal cells having eosinophilic cytoplasms .
the ameloblastomatous pattern is the least common and has palisaded ameloblastomatous cells at the periphery of clear cell nests . the case that we report was characteristic of the monophasic pattern .
ccoc must be distinguished histopathologically from clear cell carcinoma arising from salivary glands and other benign odontogenic tumors which may also have clear cells , like ameloblastoma and calcifying epithelial odontogenic tumor .
metastatic tumors , such as metastatic renal clear cell carcinoma must also be ruled out .
the presence of perineural or vascular invasion is an indicator of malignancy and can be used to identify ccocs .
the treatment of choice as agreed upon by most authors is wide excision of the tumor , including the adjoining soft tissue when involved .
the recurrence rate following such treatments appears to be much lower than when treated by enucleation or curettage .
elective neck dissection has been performed by several authors and it is interesting to note that none of these patients had recurrences .
adjuvant radiation therapy is generally considered in cases with extensive soft tissue invasion , perineural spread , lymph node metastasis with extra nodal involvement or in those where tumor - free margins are not possible .
long - term follow - up of patients with ccoc is imperative in view of the aggressive biological potential .
clear cell odontogenic carcinoma ( ccoc ) is a rare aggressive tumor that has the ability to invade locally as well as cause regional and distant metastasis . 
 the etiology of this neoplasm remains poorly understood and the diagnosis of ccoc is done by exclusion of other clear cell tumors . to date , 
 approximately 75 cases of ccoc have been described in the english literature , all involving a single jaw . 
 the majority of cases have been reported to arise from the mandible , the maxilla is less frequently involved , and no case had involvement of the temporomandibuar joint . 
 lymph node metastasis at initial presentation is reportedly rare ( < 10% ) . 
 we describe possibly the first case of ccoc in a 50-year - old woman with involvement of the mandible and the temporomandibuar joint along with cervical lymph nodal metastasis . 
 we share our experiences and challenges in the management of this unusual tumor .