Parosteal osteosarcoma: Report of a rare juxtacortical variant of osteosarcoma affecting the maxilla

Parosteal osteosarcomas are rare, low-grade juxtacortical variant of osteosarcoma, especially in the jaws, representing 1.6% of all bony malignant tumours and upto 5% of all osteosarcomas. Only 12 cases of intraoral parosteal osteosarcomas have been reported in the English literature. In the jaws males are more commonly affected with peak occurrence at 39 years and nearly equal site predilection for maxilla and mandible. Radiographically, parosteal osteosarcomas are radiodense, lobulated masses with a broad stalk to the cortex of the bone with no periosteal reaction and medullary invasion. Microscopically, shows well-differentiated tumor with minimum atypia and rare mitotic figures separating trabeculae of woven bone. Unlike classical and periosteal osteosarcoma, it is considered to have a good prognosis. A case report of this rare entity in 22-year-old female patient with bony hard, painless swelling of 9 months duration in maxillary premolar-molar region is presented. The need for differential diagnostic approach is emphasized from other seemingly benign clinical entities.