salivary gland carcinomas located centrally within the mandible are rare , comprising less than 0.4% of all salivary gland carcinomas . mucoepidermoid carcinomas are the most frequently reported types of primary central salivary gland carcinomas of the mandible followed by adenoid cystic carcinomas ( acc ) , adenocarcinomas and acinic - cell carcinomas . acc which is so rarely seen in the jaw bones usually occurs in the posterior mandible of adults in 4 to 6 decade , causing pain due to peri - neural invasion . it is well known for its prolonged clinical course and its tendency for delayed onset of the distant metastases . when such neoplastic transformation occurs centrally within the mandible , the radiological and clinical presentations may mimic odontogenic tumors making their diagnosis troublesome . hence , regardless of the histology the diagnosis should rely on the application of strict diagnostic criteria . we hereby report a case of primary intraosseous acc atypically involving whole of the mandible with no distant metastasis in spite of its unusual size . literature search on pubmed did not reveal any acc case with such an extensive involvement of mandible . a 64-year - old male patient reported to the outpatient department with the chief complaint of pain in the lower jaw . gingiva appeared inflamed due to chronic generalized periodontitis with no other evident change in the mucosa . panoramic radiograph [ figure 1 ] and intraoral periapical radiographs showed an irregular lytic lesion involving almost whole of the mandible . panoramic radiograph showing lytic lesion with irregular margins involving complete body and ramus of the mandible the possibility of a malignant tumor was considered based on the clinical findings . on performing incisional biopsy , histopathological findings showed predominantly solid , tubular and cribriform pattern in very few areas . the tumor cells were basaloid in nature with scanty cytoplasm and oval to round nucleus . majority of the areas ( > 30% ) showed solid pattern , hence the diagnosis of solid adenoid cystic carcinoma was made . to rule out the possibility of local and distant metastasis , subsequent examination including ultrasound scanning ( usg ) , computed tomography ( ct ) , distant metastasis was ruled out with no other lesions of the major or minor salivary glands . considering the size and bilateral extension of tumor , subtotal mandibulectomy ( sparing the condylar stumps ) along with bilateral suprahyoid neck dissection was planned as tumors > 4 cm have been associated with an unfavorable outcome . due to its peculiar clinical presentation , adequate soft tissue margin was removed prophylactically on both buccal and lingual aspect of the lesion . histopathology of the excised specimen showed intraosseous involvement of solid variant of adenoid cystic carcinoma [ figures 2 and 3 ] , lymph nodes and excised salivary glands were negative . follow - up after 15 months since the initial diagnosis showed no sign of recurrence . histopathological image of decalcified section showing intraosseous involvement of solid pattern of adenoid cystic carcinoma ( h&e stain , 100 ) histopathological image showing tumor cells arranged in solid pattern with few cells showing abnormal mitosis ( h&e stain , 400 ) axial ct showing extensive lytic ( low density ) lesion involving complete body and ramus of mandible central salivary gland neoplasms are extremely rare , acc ( 12 cases ) is the second most common histological sub type in the mandible preceded by mucoepidermoid carcinoma ( 60 cases ) . the most common site is posterior body or angle of the mandible . in 1979 , batsakis proposed a diagnostic criteria for central salivary gland neoplasm : ( 1 ) radiographic evidence of osteolysis , ( 2 ) presence of intact cortical plates , ( 3 ) presence of intact mucous membrane overlying the lesion , ( 4 ) absence of any primary tumor within major or minor salivary gland , ( 5 ) histological confirmation of the typical architecture and morphological features of a salivary gland tumor . in our case , it was thought that the tumor first occurred in the mandible , and later expanded widely throughout the medullary spaces of the mandible . some theories propose the following : ( 1 ) enclaved retromolar mucous glands during embryological development of the jawbones , ( 2 ) submandibular and sublingual glands closely apposed in bony defects or cavities in the lingual cortex of the mandible , or ( 3 ) fragments of submandibular and sublingual glands that have undergone embryologic evagination . histologically , the cribriform or tubular growth patterns is associated with a better prognosis , in contrast presence of ( > 30 - 50% ) solid areas indicates an aggressive clinical course . according to brookstone and huvos , lesions that are located within undisturbed , intact cortical bone and overlying periosteum and that show no signs of cortical expansion offer the best prognosis and therefore indicate stage i disease . stage ii disease is characterized by lesions surrounded by intact cortical bone that has undergone some degree of expansion . an instance of cortical perforation , breakdown of the overlying periosteum or nodal metastatic spread is categorized as stage iii disease . radiographically , the lesions , in general , are poorly defined and have infiltrative margins . the center of the lesion , as was the case with our patient [ figure 4 ] , usually show low density on the computed tomography ( ct ) scan and radiograph . acc infrequently occupies almost the whole area of a sparse component without any influence on surrounding structures , as seen in our case . the changes on magnetic resonance ( mr ) images are characterized by an increase in intensity with maintenance of the shape . ct and mri play a pivotal role in predicting the peri - neural spread and submucosal extensions . the differential diagnosis for acc should include polymorphous low - grade adenocarcinoma ( plga ) , basaloid squamous carcinoma ( bsc ) , mucoepidermoid carcinomas , acinic cell carcinoma and malignant mixed tumors , adenocarcinoma and squamous cell carcinoma . plga shows similar histological patterns ( solid , cribriform and tubular ) , growth pattern and peri - neural spread . polymorphous architecture , single file / single cell infiltration and foci of papillary growth are some of its main characteristic features . histological features of high grade i.e. increased mitotic figures , coarse chromatin , apoptosis and necrosis are commonly associated with acc ( solid ) than plga . both tumors produce basement membrane like material , but the latter tends to dissect between tumor cell rather than forming cribriform spaces . necrosis and basaloid cells with prominent nucleoli and coarse chromatin are common features , although single cell necrosis , rapid mitotic rate and greater degree of nuclear atypia are more frequent in bsc . it ranges from enucleation or curettage to en bloc or radical excision , but no method of treatment reduces the potential for recurrence . our patient is being regularly followed up for any evidence of recurrence or distant metastases since 15 months from the original diagnosis . however , long - term follow - up is indispensable regardless of the site because of the tumor 's susceptibility for late recurrence and metastasis . in the present case , acc had spread to involve almost whole of the mandible . in spite of the size , no metastasis was discovered , which otherwise , is a common finding in such cases . the extensive involvement of the mandible could possibly be due to the insidious clinical course that characterizes acc as it infiltrates nerves , peri - neural spaces and tissue planes . although salivary gland tumors arising within the mandible are uncommon , their significance should not be minimized . because of their unique morphology and clinical behavior , they should be considered in the differential diagnosis of aggressive lesions of the mandible . if intraosseous acc is suspected , a multidisciplinary diagnostic approach should always be adopted . although in our case , there is no recurrence after 15 months , long term follow - up is essential for acc in order to avoid metastasis in addition to recurrence of this lesion . this case underlines the importance of early detection , total surgical resection and long - term follow - up as it is essential in clinical management due to their higher recurrence rate .
the primary central salivary gland neoplasms of the mandible are infrequent . 
 their clinical and radiographic features may be similar to odontogenic tumors , which are otherwise common . 
 their accurate diagnosis becomes troublesome . 
 hence , diagnosis should depend on stringent diagnostic criteria . 
 adenoid cystic carcinoma is well known for its prolonged clinical course and its tendency for delayed onset of distant metastases . 
 the long - term survival of these patients is therefore poor . 
 treatment modalities include surgery , radiotherapy and chemotherapy . 
 the purpose of this paper is to report a case of primary central adenoid cystic carcinoma of mandible with an atypical presentation .