lipoma is the most common soft tissue mesenchymal neoplasm in adults , which is located in any part of the body .
the majority occurs in the upper - half of the body , particularly the trunk , head , and neck region , and it is rarely described in the oral cavity .
conventional lipoma has been divided into three forms according to the origin of the localization : superficial lipoma ( arise within subcutaneous tissue ) , deep lipoma ( arise within deep soft tissue ) and parosteal lipoma ( arise within the surfaces of bone ) .
the histological characteristics and types vary , which include angiolipoma , angiomyolipoma , myolipoma , osteolipoma and chondrolipoma .
both osteolipomas and chondrolipomas are rare entities.[24 ] however , occurrence of osteolipomas or in other term  lipomas with oseous and cartilagenous metaplasia  are less common than other subtypes of lipomas .
the term of osteochondrolipoma has been used for the lipomas containing both cartilage and bone which , are very rarely seen and generally associated with a paraosteal localization . to our knowledge ,
a 64 year old male patient with painless mass on his mandibulary symphysis region , was referred to the department of oral and maxillofacial surgery , faculty of dentistry on september , 2007 .
the lesion had been first noticed 2 months prior of the presentation to the clinic with no significant enlargement .
clinical examination of the oral cavity revealed a well demarcated , firm , round and exophitic lesion of approximately 2 cm in diameter at the symphysis region of the left mandible .
the lesion was firmly attached to the bone in the clinical examination and the overlying mucosa was intact and of normal color .
radiographically , at the site of the lesion some degree of radioopacity was observed [ figure 1 ] . under local anesthesia ,
the patient was taken to the operating room and the lesion was completely excised with an intraoral approach . during the surgical intervention ,
the encapsulated lesion was not adherent to the underlying periosteum and overlying mucosa , thus the lesion was dissected and removed easily [ figure 2 ] .
the surgical specimen was histopathologically evaluated for final diagnosis at department of oral pathology , faculty of dentistry , gazi universitys . the 6-month postoperative follow - up showed healing of the oral mucosa without any recurrency .
preoperative panoromic radigoraph exhibiting the dense radioopacity ( arrow ) in the symphysis region of the mandible intraoperative view of the lesion with encapsulation macroscopically , the gross specimen was a 2.7  1.8  1.4 cm encapsulated mass mostly comprising of adipose tissue with a few number of encapsulated nodular structures . on section ,
focal areas of hyaline chondroid structures and lamellar bone with fatty marrow were seen throughout the lesion .
both islands of bone and cartilage were surrounded with well defined fibrous tissue [ figure 3 ] .
there was no histological evidence of malignancy , such as mitosis , cellular atypia , necrosis , and hemorrhage .
histochemistry with alcian blue periodic acid - schiff stain showed acid mucopolysaccaride presence in chondroid tissue ; hence , this was hyaline chondroid .
on immunohistochemistry , adipocytes were positively stained with vimentin antibody , while both adipocytes and chondrocytes were positive for s-100 protein [ figure 4 ] .
histopathological features of osteochondrolipoma showing mature adipose tissue containing cartilage islands and lamellar bone trabecules ( h and e , 40 ) chondrocytes and adipocytes demonstrating positivity for s 100 protein ( immunoperoxidase , 40 )
however , they are relatively uncommon in the oral cavity with incidence of 14% . variants of lipoma especially osteolipoma and chondrolipoma are very rare lesions which are located in the oral cavity .
furthermore , intaoral lipoma with both osteoid and cartilaginous metaplasia has been reported just in two cases .
we presented an osteochondrolipoma case that differed from the typical arrangement by two rare alterations .
first , the lesion showed well - defined cartilaginous and osseous areas within lipoma that is also considered as osseous and cartilaginous metaplasia . in the a study of fregnani et al .
, fibrolipoma was reported as the dominant subtype in 46 lipoma cases , in which neither osteolipoma nor chondrolipoma was found .
two lipomas with cartilaginous or osseous metaplasia was reported out of 125 lipoma cases in another study , whereas none of the cases represented osteochondrolipoma .
although , any case in the name of  oral osteochondrolipoma  has not been reported , lipoma with osteoid and cartilaginous metaplasia has been represented by two cases in the oral region .
the osteochondrolipoma is the specific term of the lipoma with mature cartilaginous and osseous differentiation ; thus , both terms represents the same entity .
some authors consider such type of lipoma as a benign mesenchymoma due to consisting of two or more mesenchymal elements such as lipocytes , chondrocytes , osteocytes , and fibroblasts .
jones et al . stated that the term of benign mesenchymoma should be used strictly to describe an unencapsulated neoplasm composed of two or more mature mesenchymal tissues not ordinarily associated with each other , excluding fibrous connective tissue . in the present case ,
as the tumor is well demarcated and partially encapsulated and moreover the prominent component is mature adipose tissue , the tumor is considered as osteochondrolipoma .
second alteration that took part in this case , was the parosteal localization of the lesion .
the parosteal lipoma which is defined as lipoma exhibits a conguous relationship with the periosteum , usually demonstrating some form of attachment to periosteum with an underlying osseous reaction , is rarely seen in the oral cavity .
various types of osseous cortical responses from a reactive overproduction of bone to cortical erosion can be seen underlying bone .
the radiopacity in our case may reflect either the reactive bone production of underlying bone or the density of cartilagenous and ossous component of the tumor .
multipotent cells of mesenchyme , different cell lines and metaplastic differentiation of the adipose tissue are three hypothesis regarding the origin of the tumor .
however , considering its parosteal location , histological findings of well - formed cartilage and bone tissue within the adipose tissue neoplasm , it is decided to be a true neoplasm of mesenchymal tissue stem cells showing characteristics of three different tissues originating from the mesenchyme .
 osteochondrolipoma is a rare benign soft tissue neoplasm . 
 it is occasionally considered to be a variant of adipose tissue neoplasm  
 lipoma showing multiple differentiation pathways of pluripotent stem cells . as with the lipomas they can be seen at any location and 
 show cartilagenous and osteoid differentiation when located parosteally . 
 we present a case of osteochondrolipoma located at the symphysis of the mandible . to our knowledge , this is the first reported case of an oral osteochondrolipoma associated with parosteal localization . 
INTRODUCTION
CASE REPORT
DISCUSSION