Osteosarcoma
Osteosarcoma is a malignancy of the mesenchymal bone producing/forming cells.
Osteosarcoma most commonly occurs in the long bones of the extremities. Around 6-7% occur in the jaws.
ETIOLOGY
The etiology of osteosarcoma is unknown. However, there are some predisposing factors that have been implicated in playing a role in development of osteosarcoma:
Rapid bone growth during the adolescent growth spurt
Hormonal factors
Bone dysplasias --> Fibrous dysplasia, Paget's disease, hereditary multiple exotosis
Li-Fraumeni syndrome
Rothmund-Thomson syndrome
Genetic defects/aletrations --> RB1 gene, p53 gene.
TYPES OF OSTEOSARCOMA
Central or Conventional --> Lesion occurs in the medullary cavity; is the most common type.
Surface or Juxtacortical --> There are two types of "surface" lesions:
1) Paraosteal type --> Lesion is exophytic, nodular mass and shows no periosteal elevation or reaction. This type rarely occurs on the jaws. 2) Periosteal type --> Lesion occurs in between the cortex and inner layer of the periosteum, leading to a periosteal elevation.
Extra-skeletal --> Lesions arise in the soft tissue; very rare.
CLINICAL FEATURES
Osteosarcoma most commonly affects young people between 10-25 years and usually occurs in the long bones.
Osteosarcoma of the jaws (gnathic osteosarcoma) represent 6-7% of the all osteosarcoma cases.
Interestingly individuals affected with gnathic osteosarcoma are in the 3rd to 5th decade age group, with the mean age being 33 years.
Gender -> Slight male predilection.
Site -> Osteosarcoma has been reported to have a slightly higher predilection for the mandible.
Sites frequently involved in the mandible -> lesions frequently occur in the body of the mandible followed by the angle and symphysis.
Sites frequently involved in the maxilla -> alveolar ridges and sinus.
Most common manifestation of gnathic osteosarcoma is swelling of the jaws (hard swellings of the buccal and lingual cortices), facial deformity and pain.
Tooth loosening/mobility/seperation and parasthesia are also fairly common findings.
Maxillary osteosarcomas may cause nasal obstruction, epistaxis and proptosis.
Patients may manifest with trismus -> limited mouth opening.
RADIOLOGY FEATURES
Radiographic appearance of osteosarcoma shows variable findings.
The lesion may range from being radiolucent, radiopaque and mixed radiolucent-radiopaque.
A significant radiographic finding (in early stage osteosarcoma) to help in diagnosis is a symmetric widening of periodontal ligament space.
Advanced lesions may show moth-eaten radiolucencies or irregular radiopaque findings. However, most lesions are usually mixed radiolucent-radiopaque.
Around 25% of osteosarcoma lesions show a "sunray" or "sun-burst" pattern or appearance (streaks of bone/calcification radiating outward from the lesion).
The periosteum may sometimes elevate over the tumor in a tent like fashion. This is called Codman triangle and usually occurs in the tumor of the long bones.
💡Know Thy Facts!
Uniform/symmetric widening of periodontal ligament spaces is also seen in Scleroderma.HISTOPATHOLOGY FEATURES
Histopathology shows tumor cells that are round to spindle shaped mesenchymal cells (these are basically, malignant osteoblasts or osteoblast precursors).
The tumor cells produce an irregular pattern of osteoid.
However, they may also produce chondroid (cartilage like material) and fibrous tissue.
Hence depending on the amounts of osteiod, chondroid and fibrous tissues, osteosarcoma, histologically is calssifed as a) Osteoblastic, b) Chondroblastic and c) Fibroblastic subtypes.
The mesenchymal tumor cells are pleomorphic with varied cell and nuclear shape and size.
TREATMENT
Treatment may require radical mandibulectomy or maxillectomy (depending on the site).
Advanced cases may respond more favorably with pre-operative chemotherapy followed by radical surgery.
Mandibular tumors have better prognosis than maxillary tumors.
Prognosis highly depends on complete removal/resection of the tumor.
✅HIGHLIGHTS - VIVA & ENTRANCE EXAM PERSPECTIVE
Bone dysplasias like Fibrous dysplasia and Paget's disease are predisposing/risk factors for the development of osteosarcoma.
Osteosarcoma has been reported to have a slightly higher predilection for the mandible.
In the mandible, lesions mainly occur in the body of the mandible.
Most common manifestation of gnathic osteosarcoma is swelling of the jaws (hard swellings of the buccal and lingual cortices), facial deformity and pain.
A significant radiographic finding (in early stage osteosarcoma) to help in diagnosis is a symmetric widening of periodontal ligament space.
Advanced lesions may show moth-eaten radiolucencies or irregular radiopaque findings.
Around 25% of osteosarcoma lesions show a "sunray" or "sun-burst" pattern or appearance.
The periosteum may sometimes elevate over the tumor in a tent like fashion. This is called Codman triangle.
Histologically, the tumor cells produce an irregular pattern of osteoid.
Depending on the amounts of osteiod, chondroid and fibrous tissues, osteosarcoma, histologically is calssifed as a) Osteoblastic, b) Chondroblastic and c) Fibroblastic subtypes.
REFERENCES AND FURTHER READING
Chaudhary M, Chaudhary SD. Osteosarcoma of jaws. J Oral Maxillofac Pathol. 2012;16(2):233-238.
Kalburge JV, Sahuji SK, Kalburge V, Kini Y. Osteosarcoma of mandible. J Clin Diagn Res. 2012;6(9):1597-1599. doi:10.7860/JCDR/2012/3922.2574
Neville BW, Damm DD, Allen CM, Chi A. Oral and Maxillofacial Pathology. South Asian ed. Elsevier; 2016.
Regezzi JA, Sciubba JJ, Jordan RCK. Oral Pathology: Clinical Pathologic Correlations. 5 th ed. Elsevier; 2007.
Rajendran R, Sivapathasundaram B. Shafer’s Textbook of Oral Pathology. 7th ed. Elsevier; 2012.
Sapp JP, Eversole LR, Wysocki GP. Contemporary Oral and Maxillofacial Pathology. 2 nd ed. Mosby; 2004.