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the masticator space is an anatomical and functional entity centered on the mandibular ramus dividing it into medial and lateral compartments .
it is separated from the adjacent face and neck fascia by a superficial layer of deep cervical fascia except superiorly , where it freely communicates with the external temporal fossa , which is considered as an upper extension of masticator space .
adjacent to the masticator space are the buccal space anteriorly , parotid space posteriorly , the parapharyngeal space medially , the submandibular and sublingual space inferiorly and the base of skull superiorly .
the masticator space contains four muscles of mastication ( masseter , medial and lateral pterygoid and temporalis ) , the ramus and posterior potion of the body of mandible , the maxillary vessels and the mandibular and maxillary branches of the trigeminal nerve .
pleomorphic adenomas ( pa ) are the most common benign tumors of major salivary glands representing about 3% of neoplasms of head and neck region .
less than 5% of all juvenile head and neck tumors have their origin in salivary glands .
pas arising from ectopic salivary gland tissues may have an array of unusual locations , e.g. along the cheek , along the stenson 's duct , in accessory parotid tissue , that is separated from the body of the gland , in the floor of mouth , retromolar region , throat , alveolar mucosa , in parapharyngeal and infratemporal spaces .
however , pa occurring in the masticator space is unusual and yet to be reported . to the best of our knowledge ,
this is the first report in the english language literature of a juvenile pa presenting in masticator space .
a 16-year - old female patient reported to our department with the complaint of swelling in the left cheek region since 6 months .
the swelling was nonpainful and was not associated with any toothache or discharge or any secondary changes [ figure 1 ] .
intraoral examination revealed a small swelling causing left buccal vestibular obliteration , extending from distal side of second premolar to maxillary tuberosity [ figure 2 ] . computed tomography ( ct ) showed a hyperdense soft - tissue mass in the left masseteric space without involvement of any hard tissue .
magnetic resonance imaging ( mri ) revealed a well - defined smooth capsular outlined left masticator space lesion [ figure 3 ] .
the lesion was located lateral to left pterygomaxillary fissure and abutting lateral margin of alveolar arch of maxilla .
it has also resulted in mild anterior bowing of maxillary antral floor . patient was sent to oral surgery department for incisional biopsy .
histopathology of incisional biopsy specimen revealed epithelial component consists of epithelial and myoepithelial cells with divergent growth patterns , including trabecular , tubular , solid , cystic and papillary architecture in a connective tissue background of myxoid in nature .
a diagnosis of pa was given and excision of the whole mass was planned out .
the incision was placed intraorally in the left vestibular region and was extended posteromedially using sharp and blunt dissection .
the complete tumor was visualized and the surface of the tumor was firm in consistency .
the complete tumor along with capsule was excised [ figures 4 and 5 ] and surgical site was irrigated with 10% betadiene mixed with normal saline in 1:1 ratio .
the tumor mass measured 38  32  36 mm in size , with a whitish , faintly lobulated and focally glistening cut surface .
the histopathological findings of the excised specimen were consistent with the incisional biopsy report [ figures 68 ] , confirming the diagnosis of pa .
post - operative healing was uneventful with maintenance of normal vestibular depth [ figure 9 ] .
extraoral view showing mild facial asymmetry on the left cheek region ( black arrow ) intraoral view showing slight obliteration of the left buccal vestibular region ( black arrow ) magnetic resonance imaging showing a well - defined smooth capsular outlined lesion in left masticator space intra - operative photograph showing encapsulated tumor mass dissected out from the masticator space excised surgical specimen h and e , section showing encapsulation ( black arrow ) , duct like structures and myxomatous stroma ( 10 ) h and e , section showing numerous duct like structures with eosinophilic coagulum and epithelial , myoepithelial cells arranged in tubular and ductular patterns against a myxomatous stroma ( 20 ) h and e , section showing hyalinization surrounding duct like structures , lined by double layered cuboidal epithelium ( 40 ) post - operative intraoral photograph showing maintenance of normal vestibular depth along with healed site from where excisional biopsy had been taken , which is marked by hyperkeratotic line ( black arrow )
approximately 90% of pas occur in the major salivary glands and 6% in the minor salivary glands .
the most common site of pa of a minor salivary gland is palate followed lip , buccal mucosa , floor of mouth , tongue , tonsil , pharynx , retromolar area and nasal cavity .
even though , pas are more prevalent in the 4 and 6 decade of life , cases of pas occurring in the 1 two decades have been reported .
case series of juvenile pas have been presented by krolls et al . , byars et al . , yamamato et al .
hence , it is essential to point out that this case report of pa arising from masticator space in a 16 year old juvenile is the 1 of its kind to be reported in english language literature . due to their unique anatomic location
the tumors of masticator space remain silent for very long time , until they attain a very large size or until they hinder any function .
the frequent clinical presentation of tumors of masticator space has been reported in superior gingivobuccal sulcus .
similarly , our patient also presented a swelling in the left cheek region , with obliteration of left maxillary buccal vestibular region , which only became more prominent while opening the mouth .
differential diagnoses in these cases include neural and vascular benign lesions , e.g. schwannoma , neurofibroma , hemangioma , lymphangioma along with other entities such as lipoma , leiomyoma , rhabdomyoma , rhabdomyosarcoma and chondrosarcoma .
masticator space is difficult to explore only by means of clinical examination ; imaging techniques , such as mri and ct , are , therefore , essential in order to correctly evaluate this region .
ct scan and mri were proved as significant diagnostic tool in our case determining the extent and boundaries of lesion along with local spread and bony erosion of adjacent tissue .
the tumor has three components : an epithelial cell component ; myoepithelial cell component ; and a stromal ( mesenchymal ) component .
the identification of these three components , which may vary quantitatively from one tumor to another , is essential to the recognition of pa .
histologically pa presents with variable pattern of epithelium in a loosely fibrous stroma , which may be myxoid , chondroid or mucoid .
the epithelium is usually arranged in sheets or strands and ductal structure , often bilayered , are atypical .
these cells are as typical as to almost diagnostic and their presence in small biopsies is helpful . in most instances ,
however , immunohistochemistry may be supportive and helpful in delineating the different cell types and components , as well as in differentiating pa from other tumors .
the following immunohistochemical stains have proven to be helpful ; keratin - positive in luminal epithelial and abluminal basal / myoepithelial cells , cam 5.2 and epithelial membrane antigen positive in luminal epithelial cells , p-63-positive in abluminal basal and myoepithelial cells , calponin , maspin , s-100 - positive in myoepithelial cells .
regarding the origin of pa in the typical location as in our case , it can be suggested by the presence of heterotrpic salivary gland tissue in masticator space .
ferlito et al . , in his study , have suggested various locations for ectopic salivary gland tissues such as pituitary glands , external auditory meatus , nasal fossa , sterno - clavicular joint , mandible and cervical soft tissue . even though , there exists an anatomic proximity between deep lobe of parotid and masticator space , but the probability of deep lobe pa spreading to masticator space can be ruled out in our case through revelation done by ct scan images , which suggested tumor arising denovo in masticator space region by showing a fine lucent line representing compressed layer of fibroadipose tissue between tumor and deep lobe of parotid . in our case ,
a modified approach was made with vestibular incision without any osteotomy and taking the whole capsulated tumor in toto .
the prognosis of pa is good and the chances of recurrences are rare in pa arising from minor salivary glands ( 3.4% recurrence in 5 years ) .
long - term follow - up is mandatory in younger patients to ensure disease free period .
however in our case due to its location in masticator space , only periodic clinical follow - up is insufficient and it should be supported by radiological and ct scans evaluation to detect any recurrences . in our case ,
pleomorphic adenoma ( pa ) , also called benign mixed tumor , is the most common tumor of the salivary glands . 
 about 90% of these tumors occur in the parotid gland and 10% in the minor salivary glands . 
 juvenile pas are uncommon and about 5 - 10% of minor salivary gland pa affects patients aged 20 years and under . 
 the most common sites of pa of the minor salivary glands are the palate followed by lips and cheek . 
 other rare reported sites include the throat , floor of the mouth , tongue , tonsil , pharynx , retromolar area and nasal cavity . 
 the masticator space is a deep facial space with a complex anatomical structure where pa is not known to occur . here 
 , we report an unusual case of pa of left masticator space in a 16-year - old girl patient , which to the best of our knowledge is the first reported case in english language literature .