Odontogenic Myxoma of Mandible Appeared as an Ameloblastoma on CT Imaging

Odontogenic myxoma is a rare benign tumor of ectomesenchymal origin, which can arise from dental papilla, follicle or periodontal ligament. Most commonly it arises from mandible followed by maxilla. We report a case of odontogenic myxoma in a 23 years old female who came with complaint of painless swelling in left mandible. CT scan revealed an expansile radiolucent lesion involving the left mandible body with cortical thinning and mild destruction at few places. Biopsy was done which was suggestive of odontogenic myxoma. Surgery was done and odontogenic myxoma was proved on the biopsy.


INTRODUCTION
Odontogenic myxoma is a capsulated tumor of jaw. It is slow growing tumor, usually painless however it is locally aggressive. It may result in extensive osseous destruction and cortical expansion. CT appearance of odontogenic myxoma is lucent lesion with multiple radiopacities. Ameloblastoma is locally aggressive odontogenic tumor. ameloblastoma give variable appearance which may be solid, unilocular or multilocular cyst.

CASE REPORT
A 23 years old female had come with the painless swelling involving the left mandible since last 4 months. On clinical examination there was a swelling seen posterior to the 2 molar tooth, which is displaced antero Intraoral and panoramic radiography reveled an expansile radiolucent lesion involving the body the mandible posterior to 2 nd molar tooth on left side. CT scan was done for further evaluation, which showed an expansile hypodense involving the body of left mandible (Fig There were few fine trabeculations also seen in the inferior aspect (Figs. 1 A and thinning of the cortex seen with interruption of the cortical plate continuity at few places C). Ameloblastoma was given as the likely diagnosis; differential diagnosis of odontogenic myxoma was given. Biopsy was done which was suggestive of odontogenic myxoma. excision surgery was done and histopathology revealed the tumor was composed of loosely arranged, spindle shaped and stellate cells in myxoidstroma which is consistent of odontogenic myxoma (Fig. 2).
Recontruction surgery of the mandible was also done.

DISCUSSION
Prevalence of Odontogenic myxoma accounted to be 0.04% to 3.7%, of which 0.5% to 17.7% of cases have been reported in America, Europe and Asia [1,2]. The majority of the patients with Odontogenic myxoma are second and third decade [3].Females are twice more commonly affected than males mandible appears to be more frequently involved than maxilla, with higher predilection towards posterior regions [5]. Odontogenic rarely cross midline and are confined to one side [4]. There are no specific clinical or radiological 639 benign non It is slow growing tumor, usually painless however it is locally aggressive. It may result in extensive osseous destruction and cortical expansion. CT appearance of myxoma is lucent lesion with pacities. Ameloblastoma is locally Radiologically ameloblastoma give variable appearance which unilocular or multilocular cyst.
A 23 years old female had come with the the left mandible On clinical examination there was a swelling seen posterior to the 2 nd which is displaced antero-laterally. Intraoral and panoramic radiography reveled an expansile radiolucent lesion involving the body of molar tooth on left CT scan was done for further evaluation, hypodense lesion involving the body of left mandible (Figs. A-D). There were few fine trabeculations also seen in and B).There was thinning of the cortex seen with interruption of the cortical plate continuity at few places (Figs.1 A & Ameloblastoma was given as the likely differential diagnosis of odontogenic done which was myxoma. Wide excision surgery was done and histopathology the tumor was composed of loosely arranged, spindle shaped and stellate cells in myxoidstroma which is consistent of odontogenic surgery of the mandible was also myxoma has been accounted to be 0.04% to 3.7%, of which 0.5% to ed in America, The majority of the myxoma are seen in Females are twice more commonly affected than males [4].The mandible appears to be more frequently involved than maxilla, with higher predilection towards [5]. Odontogenic myxoma rarely cross midline and are confined to one side [4]. There are no specific clinical or radiological signs that would allow a physician to distinguish myxoma from odontogenic and nonodontogenic lesions, thereby making its diagnosis even more difficult. Odontogenic myxoma odontogenic tumors, which originates from the mesodermal portion of the odontogenic apparatus [6]. They are benign, slow growing tumors usually asymptomatic and painless. Although some patients present with progressive pain in lesions due to local invasion into surrounding soft tissue structures with eventual neurological disturbances leading to osseous destruction and cortical expansion Odontogenic myxoma of the maxilla is less frequent but behaves more aggressively t that of the mandible [5]. When patient present with swelling of jaw first investigation is panoramic radiography, however if swelling is hard and fixed to adjacent tissue CT scan is necessary to evaluate the contour of the lesion, it's content and extent in the adjacent tissue. Radiographically, odontogenic myxoma lesions appear as radiolucent lesions separated by bony trabeculae that form geographic compartments [8]. They may appear as a unilocular or multilocular radiolucency with characteristic "honeycomb", or "soap-bubble" pattern with cortical expansion and tooth displacement signs that would allow a physician to distinguish myxoma from odontogenic and nonodontogenic lesions, thereby making its diagnosis even more myxomas are true which originates from the mesodermal portion of the odontogenic They are benign, slow growing tumors usually asymptomatic and painless. Although some patients present with progressive in lesions due to local invasion into surrounding soft tissue structures with eventual neurological disturbances leading to osseous destruction and cortical expansion [1,7]. myxoma of the maxilla is less frequent but behaves more aggressively than When patient present with swelling of jaw first investigation is panoramic radiography, however if swelling is hard and fixed to adjacent tissue CT scan is necessary to evaluate the contour of the lesion, nt in the adjacent tissue. myxoma lesions appear as radiolucent lesions separated by bony trabeculae that form geographic compartments They may appear as a unilocular or diolucency with characteristic bubble" pattern with cortical expansion and tooth displacement [4].
axial CT scan of the patient showing a unilocular radiolucent g the body of the left trabeculations seen at inferior cortical thinning with cortical destruction seen at some places Differential diagnoses include ameloblastoma, ameloblastic fibroma, odontogenic fibroma, central hemangioma, or odontogenic keratocyst aneurysmal bone cyst, central giant cell granuloma, mestastatic tumor and, in cases of unilocular lesions, simple cysts [4,5].
Ameloblastoma are benign however locally aggressive tumors, it arises from the surface epithelium, remnent of dental lamina or pleuropotential epithelial cells. Almost 10% odontogenic tumors are ameloblastoma in which 80% are located in the mandible [8]. Approximately 5% ameloblastoma arises from the epithelial lining of dentigerous cyst [8]. It shows variable radiological features, which depends on it's histology. Solid or multicystic appearance is most common which are seen in 80% of the ameloblastoma. Typical appearance on CT scan is multicystic lesion in mandible with internal septations, honeycomb or soap bubble appearance. May present with a unilocular cyst with impacted tooth, these findings may resemble dentigerous cyst. However presence of solid component and internal septae help in differentiate the lesion with dentigerous cyst [9].In our case there is an expansile lytic lesion with cortical erosions and trabeculations, so these findings can be seen in ameloblastoma and odontogenic myxoma. It was painless swelling and ameloblastoma and odontogenic myxoma both are usually painless. In few cases when aggressive local invasion occur they can present with pain.

Fig. 2. Pictomicrograph odontogenic myxoma showing the spindle shaped and stellate cells in myxoidstroma
A biopsy is necessary to ascertain an accurate diagnosis. Ododntogenic myxoma shows little encapsulation histologically and often extends into the soft tissue through the bony structures, so that complete resection is difficult and recurrence is common [10]. Since they tend to infiltrate and recur, they are most commonly treated with wide margin surgical resection [11]. The conservative management of myxoma; excision and curettage with liquid nitrogen cryotherapy, is an alternative method proposed to radical resection. In this, liquid nitrogen is used which will eliminate any remaining neoplastic cells by bone devitalization without affecting the inorganic structure, thereby yielding new bone formation. However, a minimum of five years of surveillance is required to confirm that the lesion has healed, and periodical clinical and radiographic follow up should be maintained indefinitely irrespective of treatment modality applied to treat odontogenic myxoma [5].

CONCLUSION
Odontogenic myxomas are rare odontogenic tumors. These tumors are difficult to differentiate with ameloblastoma on radiological findings. Clinical findings and pathological findings are necessary to reach the diagnosis. However the role of CT scan is important to evaluate the extent of the lesion and cortical erosions.

CONSENT
Authors declare that 'written informed consent was obtained from the patient for publication of this case report and accompanying images.

ETHICAL APPROVAL
Approval from the ethical committee of the hospital was obtained.