schwannoma is a benign nerve sheath tumor originating from schwann cells , and is known as neurilemmoma and neurinoma . although the head and neck region is a rather common site for these benign lesions , intraoral schwannomas , especially the intraosseous types , are very rare , and can account for less than 1% of the benign intraosseous neoplasms .
the clinical and radiographic findings of intraosseous schwannoma may be similar to many other lesions such as odontogenic cysts and other benign tumors .
therefore , various differential diagnoses have been proposed , which may lead to some sort of confusion in its diagnosis . according to the observation in the literature ,
these lesions are more common in the mandible and among females , which are mostly observed in the 2 and 3 decades of life . here , along with a review of the related literature , we try to present a case of intraosseous schwannomas that has been recognized in a 9-year - old boy .
the patient was a 9-year - old boy who was referred to the department of oral and maxillofacial pathology of the isfahan university of medical science 5 months ago , while complaining about a swelling in the inferior border of the right mandible .
deviation of anterior teeth and looseness of teeth ( d , e ) were seen . in the panoramic radiograph ,
radiolucency with sclerotic border from mesial of tooth 36 to distal of 3c and transposition of first and second impacted premolar was observable [ figure 1 ] .
radiolucency with sclerotic border from mesial of tooth 36 to distal of 3c in the panoramic radiogeraph axial computed tomography scan revealed a unilacular lesion in the left mandibular body , 2.5  3 cm in size , with a well - defined border , marked expansion and thinning of the buccal and lingual cortical plates [ figure 2 ] .
unilacular lesion in the left mandibular body , 2.5  3 cm in size , with well - defined border in axial ct scan first , on the basis of clinical and radiographic features , we can suggest the following lesions : keratocystic odontogenic tumor , central giant cell granuloma , unicystic ameloblastoma and ameloblastic fibroma .
excisional biopsy was performed and irregular masses of solid tissues were observable during biopsy . in the histopathology features , ovoid to spindle shape and epithelioid cells were identified , some of which indicated slight pleomorphism and hyperchromatism
besides , some regions showed intracellular edema and degenerative changes . in some parts , numerous blood vessels and perivascular hyalinization
antoni a : palisading arrangement of spindle cell , verocay body , antoni b : spindle cells haphazardly distributed in a delicate fibrillar matrix .
h and e : original maginifiction ( 40 ) based on histopathologic features , several differential diagnoses were first taken into account : benign fibroblastic tumor , benign neural tumors and neoplastic vascular lesions . in order to reach final diagnosis , immunohistochemical staining was carried out .
the findings revealed that the intensity of s100 staining was 4 + and those of ki67 was weak and 10% at most [ figure 4 ] . according to these studies and immunohistochemistry , and regarding clinical and radiographic features and hematoxylin and eosin , in which there were some regions similar to antoni a with palisading cells and similarities of some regions to antoni b , we reached the final and definite diagnosis of the lesion .
original maginifiction ( 400 ) after 4 months , the patient was evaluated by taking panoramic radiography , and it seems that reparative process is running within the lesion [ figure 5 ] .
although schwannoma is a benign and slow growing tumor , and it is usually an asymptomatic one , almost 50% of the cases have been reported with pain .
the most common site of this tumor in the head and neck region is the tongue .
moreover , the intraosseous type is extremely rare , and accounts for less than 1% of all primary bone tumors .
average age of the people afflicted is 34 years , and the male to female ratio is 1:1.5 .
lesions are more common in the mandible than in the maxilla , and the swelling usually involves the body of the mandible .
so far , fewer than 50 cases have been recorded in the related literature , of which 44 cases have been reported by chi et al . in this report , the clinical features of these cases have been described , and only one case was younger than 10 years old .
our case is a 9-year - old boy , which appears to be extremely rare .
schwannoma can be originating from all cranial nerves , with the exception of the olfactory and optic nerves .
the tumor presents an expansive growth pattern , which may cause dislocation of teeth and may also involve the nerves .
these above - mentioned features were also observed in the case under investigation in this study .
but , the problem was that due to the scarcity of such cases , it was not possible for us to predict the schwannoma in differential diagnosis at first . in microscopic features , schwannoma is an encapsulated tumor that shows two microscopic patterns : antoni a and antoni b. streaming fascicles of spindle - shaped schwann cells characterize antoni a tissue .
these cells often form a palisaded arrangement around the central acellular , eosinophilic areas , identified as verocay bodies .
antoni b pattern is less cellular and the spindle cells are randomly arranged within a loose , myxomatous stroma .
schwannoma indicates the positivity of s100 , cd34 and ema only in capsules of the tumor . in our case
the lesion showed tumoral appearance , which was completely different from the characteristic structures of odontogenic cysts or tumors . also , specific types of cell , such as giant cells , were not obvious .
the lesion showed spindle cell pattern in most of the places , which was similar to fibroblastic or neural cells .
immunohistochemistry revealed the tumor to be positive for the s100 protein , confirming nerve origin .
on the basis of schwannoma , two characteristic patterns : observing typical limited area similar to antoni a despite verocay body was not clearly seen , and other regions akin to antoni b pattern , the diagnosis of schwannoma was made .
the present of these two important histopathologic patterns , lack of mast cells , which is one of the most helpful features in neurofibroma and also diffuse , strongly positively tumoral cells s100 expression in ihc slides , the diagnosis of nurofibroma was rejected .
it is probable that some malignant changes in schwannoma may happen , even though some malignant cases have been reported .
these changes consist of cyst formation , necrosis , hyalinization , hemorrhage , hemosiderin deposits , inflammation , fibrosis and nuclear atypia . nonetheless , these tumors are benign and atypical mitosis are never seen , and the pathologist must be cautious not to mistake these changes for evidence of a malignancy .
also , it is possible to remove the involved nerve in order to decrease the risk of recurrence .
because this lesion can be misdiagnosed clinically , radiographically and microscopically as periapical lesion , ameloblastoma , myxoma and central giant cell granuloma , careful attention should be directed toward reaching the diagnosis . only then can the appropriate treatment can be obtained .
 intraosseous schwannomas is a very rare neoplasm , and less than 50 cases have been reported in the medical literature . in this article , 
 the clinical , radiographic and histopathologic appearances of a rare case of intraosseous schwannomas are presented . 
 the importance of this case is that other benign central lesions such as odontogenic tumors and cysts might be included in differential diagnosis . 
 this case was recognized in a 9-year - old child , which is a very rare occurrence . 
 the diagnosis was confirmed by immunohistochemical staining with s100 protein . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION