osteoblastoma is a rare benign tumor that accounts for less than 1% of all bone tumors and most commonly involves the spine and sacrum of young individuals .
less than 10% of osteoblastoma are localized to skull and nearly half of these cases affecting the mandible , especially the posterior segments .
the first well - documented case of osteoblastoma of the jaw bones is attributed to borello and sedano in 1967 .
the osteoblastoma nomenclature has had a wide synonymy since its discovery by jaffe and mayer in 1932 , when it was named osteoblastic osteoid tissue forming tumor .
other names have been proposed , such as giant osteogenic fibroma and giant osteoid osteoma . in 1956 ,
the lesion was definitely separated from osteoid osteoma and recognized as an entity by jaffe and lichtenstein , in separate reports , under the name of benign osteoblastoma .
this is the name that has been adopted by the world health organization classification of bone tumors and the armed forces institute of pathology .
this central bone tumor usually occurs in young adults , with a mean age of 20 years ; with a male to female ratio of 2:1 . the lesion is characterized clinically by pain , which is traditionally said to be unresponsive to pain and swelling at the tumor site , the duration being just a few weeks to a year or a more .
radiographically the lesion may appear as radiolucent that can be either ill or well defined containing variable amounts of mineralization .
although , conventional radiography play an important role in diagnosis ; however , the final diagnosis can only be confirmed after histopathological examination .
this report describes a case of aggressive osteoblastoma in posterior segment of mandible , in a 26-year old female .
a 26-year old female reported with the chief complaint of a slowly growing painful swelling with respect to right mandibular posterior region of 3 years duration . pain associated with the swelling was mild and intermittent in nature .
extra - oral examination revealed a 3 cm  3 cm smooth - surfaced swelling involving right body of the mandible , extending from the parasymphyseal region anteriorly to the right mandibular second molar posteriorly causing obvious facial asymmetry .
the lesion contained calcified mass approximating the distal root of the second molar and few radio - opaque flecks scattered within the radiolucency .
the lesion was well - delineated , causing expansion and thinning of the lower border of the mandible [ figure 1 ] .
panoramic view revealed an expansile unilocular radiolucent lesion in relation to right mandibular second molar with variable amount of mineralization the differential diagnosis included cementoblastoma , osteoid osteoma , ossifying fibroma , and focal cemento - osseous dysplasia .
the curettings and the second molar were submitted for the histopathological examination [ figure 2 ] .
photomicrograph of the gross specimen showing curetted lesion along with the right mandibular second molar light microscopic examination of sections stained with h - e revealed irregular wove bone like tissue within areas of hypercellular and loose fibrovascular connective tissue stroma .
large amounts of osteoid and focal areas of cementoid deposition were also seen . woven bone showed large osteocytes within , along with a prominent plump osteoblastic rimming [ figures 3a and b ] .
maturation of the trabeculae could be seen at the margin of the lesion , with appreciation of demarcation from the adjacent normal bone .
photomicrograph of histopathologic section reveals irregular wove bone like tissue with osteoblastic rimming within fibrovascular connective tissue stroma .
( h - e stain ,  100 ) photomicrograph demonstrates presence of large and irregular areas of woven bone showing large osteocytes within , along with the presence of plump and even bizarre - appearing osteoblast - like cells , bordering the osteoid substance .
osteoblastoma is a rare bone forming tumor that very rarely involves the maxilla and mandible , particularly the posterior mandible .
this diagnostic challenge may cause relevant problems with the differential diagnosis in view of the tumor 's rarity , ambiguous clinico - radiologic presentation , and histopathologic features , which sometimes resemble osteosarcoma .
conventional osteoblastomas are biologically benign with limited growth potential and typically do not exceed 4 cm in diameter . however , there is a small subgroup of borderline osteoblastomas that possesses a locally - aggressive growth pattern , usually exceeding 4 cm . these tumors can not easily be classified as  conventional  osteoblastomas or osteosarcomas and have , thus , been separated from the classic lesion and designated as osteoblastoma - like osteosarcoma and malignant osteoblastomas or aggressive osteoblastomas .
the aggressive osteoblastoma occurs in the older age group than benign osteoblastoma . on the clinical side
it is able to extend into adjacent tissues and to recur in 1021% , but does not metastasize .
the histologic findings in the aggressive osteoblastoma are those that suggest the possibility of osteosarcoma rather than an obviously benign lesion .
some authors advocate that lesions described as aggressive osteoblastoma are , in fact , well - differentiated osteosarcomas resembling osteoblastomas .
the diagnostic evaluation is based on the histologic features and the clinical behavior of the lesion .
histologically and clinically , differential diagnosis for osteoblastoma ranges from a variety of benign and malignant tumors , ranging from cementoblastoma , osteoid osteoma , fibrous dysplasia , ossifying fibroma , focal cemento - osseous dysplasia , to borderline forms of the above malignancies , up to low - grade osteosarcoma .
benign cementoblastoma is to be considered in the differential diagnosis , since its radiographic features are similar to osteoblastoma .
the feature to differentiate it from osteoblastoma , however , is the merging of the lesion and the radicular surface of the tooth . in the case
described here there was no contact of the tumoral mass with the tooth , in spite of their proximity .
this microscopic similarity indicates that a lesion should not be diagnosed as benign cementoblastoma unless it adheres to the tooth .
another diagnostic pitfall in connection with the benign osteoblastoma is the possibility of its confusion with osteoid osteoma . on the clinical side
, the benign osteoblastoma does not tend to produce pain , so characteristic of osteoid osteoma . also , osteoblastoma is a larger lesion , which by definition exceeds 1 cm in its greatest diameter and is not generally associated with outstanding bony sclerosis typical of osteoid osteoma . at microscopic examination ,
the bony trabeculae of osteoblastoma are slightly wider than those of osteoid osteoma and there is less irregularity in their arrangement ; the number of osteoblasts is much greater in osteoblastoma but osteoid osteoma lacks giant cells and is not as well vascularized as osteoblastoma .
histopathologically , ossifying fibroma and fibrous dysplasia of bone may share many similarities with osteoblastoma but usually are less mineralized lesions , revealing fine calcifications rather than large clusters of mineralized material .
in addition , fibrous dysplasia is less circumscribed radiologically than osteoblastoma and may be multifocal , a feature that is exceedingly rare for osteoblastoma .
focal cemento - osseous dysplasia is a fibro - osseous lesion that may share similar radiographic features with osteoblastoma .
although microscopically , both may feature immature bone ; focal cemento - osseous dysplasia lacks a large number of plump and actively proliferating osteoblasts .
histologic examination is paramount in confirming a definitive diagnosis and excluding osteosarcoma , especially the osteoblastic variant .
the confusion arises mainly due to the presence of plump or even bizarre - appearing osteoblast - like cells in osteoblastoma , often bordering osteoid substance , mimicking the atypical cells that characterize osteosarcoma . in such instances ,
the diagnosis is greatly facilitated by the accurate interpretation of the histologic features in view of the radiologic findings that do not disclose the aggressive characteristics of osteosarcoma .
believe that the chief microscopic features that separate osteosarcoma from osteoblastoma is the lack of tumor maturation at the margins of osteosarcoma , with permeation of tumor into adjacent tissues , in contrast to maturation at the margins and lack of permeation into the adjacent bone .
further , in view of the purported benign nature of this tumor , conservative surgical excision is the treatment of choice ; because recurrence is a rare event ( 13.6% ) and usually attributable to incomplete excision .
moreover , apparently no special histological features exist that provide clues to the biological behavior of this neoplasm . based on these various reports and findings , it is clear that the neoplasm has no constant behavior , and varies from case to case .
the importance of conceiving the individual bone tumors as clinicopathologic entities should be pointed out again . in the delineation of differential entities , the clinical facts and radiologic findings are very important in the diagnostic evaluation of the lesion , and must be considered along with the histologic findings . at the same time , adequate representative sections of the entire lesion must be submitted to ensure adequate histologic diagnosis so that appropriate treatment can be instituted to the specific pathology .
 the clinical facts and radiologic findings are very important in the diagnostic evaluation of jaw swellings , and must be considered along with histologic findings . 
 osteoblastoma , an uncommon primary lesion of the bone that occasionally arises in the jaws , is one such lesion causing a localized jaw swelling . clinically , osteoblastoma can be symptomatic or even remain symptom - free , and may be diagnosed only on routine radiographic examination . 
 histologically and clinically , differential diagnosis for osteoblastoma ranges from a variety of benign and malignant tumors that poses a diagnostic dilemma . stressing the importance of the correct diagnosis of such lesions , this report discusses a case of aggressive osteoblastoma of the mandible posing as a diagnostic dilemma . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION