Low-grade osteosarcoma of the mandible

Abstract

Osteosarcoma (OS), a rare malignant bone tumour arising from primitive bone forming mesenchyme, most often arises in the metaphyses of long bones of the extremities. Bone or osteoid formation within the tumour is characteristic of an osteosarcoma. Craniofacial osteosarcoma (CFOS), most often located in the mandible or maxilla, accounts for only 5-13% of all osteosarcomas. In general, OS of the jaw is a high-grade lesion. Low-grade lesions are rare and represent less than 2% of all osteosarcomas reported in the literature. Because of its rarity and well differentiation, Low-grade OS is usually misdiagnosed as a benign lesion. The clinical and radiographic presentation does not correlate well with the subtle histology picture of a low-grade osteosarcoma which makes the diagnosis difficult.

Keywords: Craniofacial osteosarcoma; Low-grade osteosarcoma.

Fig. 1

Extraoral examination showing an ovoid shaped (6 × 4 cm in size) swelling on the right lower border of the mandible

Fig. 2

Intraoral examination showing a smooth nodular mass in the lower right alveolar ridge extending from 45–48 region

Fig. 3

Panoramic radiograph showing a diffuse mixed-density lesion, predominating radiopacity interwoven with radiolucent areas, and ill-defined margins involving the right mandible body extending from the 44–48 region

Fig. 4

Axial CT section showing a mixed density lesion of the right body of the mandible with irregular margins, cortical perforation and soft tissue infiltration

Fig. 5

Surgical resection of the tumour with safe bony margins of 2 cm

Fig. 6

Resected specimen

Fig. 7

Photomicrograph of the tumour showing a variegated appearance with proliferation of small stellate cells and spindle cells in a myxoid matrix. The cells showed moderate nuclear pleomorphism, clumped chromatin and minimal mitotic activity. A few areas of mineralization, chondroblastic differentiation of the osteoid can be seen (H&E ×400)