Imaging findings in a case of chondroblastic osteosarcoma of the mandible

Clinical History

A 40-year-old female patient presented with a 15-month history of a gradually enlarging mass in her right jaw. On physical examination a hard, immobile mass was visible in the right buccal and mandibular regions. Intraorally, it occupied the right side of the oral cavity, causing dysphonia and dysphagia.

Imaging Findings

A plain radiograph of the mandible (Fig. 1a) shows a lobulated, bony mass involving the right hemimandible. The alveolar margin cannot be delineated. It extends medially, causing displacement of lower teeth. Widening of the periodontal space in teeth 43 and 44 was also noted (Fig. 1b). The right mandibular condyle and symphysis were uninvolved.
A CT scan of the oral cavity and neck shows a 5.9 x 7.9 x 6.8 cm expansile, amorphous bony lesion exhibiting sunburst periostitis (Fig. 2). Medially, it extends into the oral cavity and sublingual space. Inferiorly, it involves the right hyoglossus muscle, and displaces the rest of the tongue contralaterally. Posteriorly, it extends to the angle of the right hemimandible, and is intimately related to the right submandibular gland.
Several enlarged lymph nodes are seen at levels IA, IB and II on the right.
Punch biopsy of the mass revealed chondroblastic osteosarcoma (Fig. 4).

Discussion

Osteosarcoma is the commonest non-haematopoietic, primary malignant tumour of bone, with an estimated incidence of 4 - 5 per million population [1]. Approximately 80% - 85% occur in long bones, particularly in femoral, humeral and tibial metaphyses [2, 3]. Conventional osteosarcoma usually occurs in the first two decades of life. Men are more commonly affected than women [1, 2]. Our case is the exception to these three commonalities.
Osteosarcoma of the head and neck is rare and tends to behave differently from conventional osteosarcoma. In 7 large series including 5, 155 cases of osteosarcoma, only 336 (6.5%) involved the head and neck. Of these, 40% occurred in the maxilla, 35% in the mandible, and 21% in the skull [2]. In the mandible such tumours usually present as a painless swelling [2, 3, 4] and are less aggressive, with a tendency for local spread rather than distant metastasis and are more frequent in women in the third or fourth decades [2, 4, 5]—characteristics seen in our patient.
The radiologic appearance of mandibular osteosarcoma is variable. These may present with a purely lytic pattern (35% - 45%), a sclerotic pattern (5%-65%), or a mixed lytic-sclerotic pattern (22% to 50%) [2]. As with osteosarcomas elsewhere, a “sunburst” pattern of periostitis is suggestive of the disease. However, this pattern is observed in only 7% to 27% of cases [2, 4]. Extraosseous soft tissue extension is common, and is seen in up to 100% of cases [2]. Symmetric widening of the periodontal ligament space is an important radiologic feature, which, together with the sunburst effect, is almost pathognomonic of the tumour [2, 6, 7].
Plain film extra-oral radiographs are often the initial imaging modality used to evaluate a jaw mass. Intraoral or panoramic radiographs provide images with less superimposition of anatomic structures [8]. Complete radiological evaluation, however, is best done with CT to determine the precise extent of the tumour, including involvement of osseous and soft tissue structures. MRI may be used, but its limited ability to image osseous findings is an important disadvantage [8]. There are no imaging findings pathognomonic of the chondroblastic type of osteosarcoma.
Wide radical resection is the treatment of choice for jaw osteosarcoma. Adjuvant chemotherapy or radiotherapy may be required in the presence of residual tumour or micrometastasis [4].

Differential Diagnosis List

Final Diagnosis

Chondroblastic osteosarcoma of the mandible

URL:	https://eurorad.org/case/15405
DOI:	10.1594/EURORAD/CASE.15405
ISSN:	1563-4086