it arises from the bone cortex as an exophytic lesion with a hyaline cartilaginous cap . oc may arise in any bone that develops from endochondral ossification and it is rare in maxillofacial region as most of the craniofacial skeleton develops from intramembranous ossification . the other reported sites are mandibular symphysis , body of mandible , in the soft tissues at the angle of the mandible , maxillary sinus and posterior maxilla . oc may present in a solitary fashion or as multiple ocs seen in autosomal dominant syndrome known as osteochondromatosis . oc occurring in the angle of the mandible is extremely rare and according to literature search , this is the only case at the angle of mandible . majority of cases are reported in condyle followed by coronoid process , four cases in symphysis region and one case is reported in angle region in the soft tissue not attached to mandible . a 18-year - old male presented to a private hospital with a chief complaint of painless slow - growing swelling since 10 years in the right side of the lower jaw . it was a solitary swelling , well - localized , measuring 4  3 cm at the angle of mandible . it projected from lower border of mandible , measuring anteroposteriorly 4 cm and superoinferiorly 3 cm , buccolingual expansion was 3 cm with a broad base . orthopantomogram showed mixed radiolucent and radiopaque lesion in the angle of the mandible [ figure 1 ] . computed tomography ( ct ) showed an irregular bony outgrowth at angle of mandible , measuring 27  25  22 mm in size , with a small irregular area of sclerosis . there were no cystic or destructive changes identified and no adjacent extraosseous soft tissue swelling or fluid collection seen [ figure 2 ] . the three - dimensional ct showed margin of the lesion to be continuous with the margins of the mandible [ figure 3 ] . radiological diagnosis of benign oc was made . under general anesthesia , through extraoral approach , the lesion at the angle of mandible was exposed [ figure 4 ] . the lesion had a broad base and an irregular surface , excision of the lesion was done along with a margin of normal bone all around . histology revealed features of oc : cancellous bone proliferation and a cartilaginous cap [ figure 5 ] . marrow spaces were filled with chondroid tissue , producing trabecular ossification [ figure 7 ] . orthopantomogram showing mixed radiolucent and radio - opaque lesion in the angle of the mandible ct image showing bony outgrowth at the angle of the mandible , with a small irregular area of sclerosis . ct = computed tomography three - dimensional ct showing , irregular bony outgrowth that is continuous with the mandibular bone intraoperative view of the tumor , at the angle of the mandible photomicrograph showing a cancellous bone with a cartilaginous cap ( h&e stain , x40 ) . h&e = hematoxylin and eosin photomicrograph showing a hyaline cartilage with cellular connective tissue stroma ( h&e stain , x100 ) photomicrograph showing a marrow spaces filled with chondroid tissue and ossifying trabeculae ( h&e stain , x100 ) oc is the most common osteogenic tumor of the axial skeleton constituting up to 50% . oc accounts for 35.8% of benign bony tumors and 8.5% of bony tumors . about 1% of these occur within the head and neck region . the growth of tumor is slow and is in coordination with the growth of the skeleton . solitary oc are exophytic lesions of bone arising from the cortex and covered by periosteum that is continuous with that of the adjacent bone and this accounts for 75% of the ocs . multiple ocs are associated with a syndrome known as osteochondromatosis or hereditary multiple exostosis ( hme ) , an autosomal dominant disorder , this account to the rest 25% of ocs . oc is frequently seen in distal metaphyseal region of long bones and also in ribs , scapulas , clavicles , vertebrae , femur and proximal metaphysis of tibia . it is suggested by lichtenstein that pluoripotent periosteum can undergo induced or spontaneous metaplasia to produce osteoblast and chondrocytes with subsequent endochondral ossification resulting in oc . histologically , oc can be diagnosed by the presence of bony trabeculae covered with a cartilaginous cap . oc should be differentiated histologically from osteoma which consists of hard dense compact lamellar bone ; benign osteoblastoma containing well - vascularized connective tissue stroma and widely dilated capillaries with active production of osteoid and woven bone ; chondroma consisting of lobules of hyaline cartilage with chondrocytes within well - formed lacunae and chondroblastoma consisting of broad areas of chondrocytes . opg is routinely used for the detection of lesions but ct , cross - sectional and three - dimensional images are of greater value which shows anatomy of lesion and surrounding area . the search showed two case reports at the angle of mandible , one case was present on the lingual surface of mandible attached with a stalk , the other reported oc was at the angle of mandible in the soft tissue and was not in continuous with the mandible . our case is unique as this oc was at the angle in continuous with the mandibular bone . this paper describes the details of a very rare case of oc arising in the angle of the mandible .
osteochondroma ( oc ) is one of the most common benign tumor of osseous and cartilaginous origin . 
 it usually occurs in the skeletal bones and very rarely in craniofacial region . in the craniofacial region , 
 condyle and coronoid process of the mandible are the most commonly affected areas . 
 the present article reports the extremely rare case of oc arising from the angle of the mandible causing facial asymmetry .