Osteosarcoma is a malignant cancer of the bone. While there are many variants of the disease, the conventional type makes up approximately 75% of diagnoses.
Signs and symptoms of this disease are those associated with typical musculoskeletal problems like pain, especially at night, and swelling. There may be pain with activity especially in the lower extremity as insuffiency pain predates overt pathologic fracture. Fevers, malaise and anorexia can be associated.
Osteosarcoma is notorious for its rapid doubling time. So patients with pain less than twelve months and swelling or mass that rapidly increasing in size should increase ones suspicion for the disease.
Children with retinoblastoma are at extremely high risk of developing osteosarcoma and should be followed as such.
Osteosarcoma is the most common bone cancer, but represents only 1% of all primary cancers. There is a bimodal prevalence of this disease. The most common age of diagnosis is in the second and third decades of life. Osteosarcoma is also found after the age of 50 often in those with Paget’s disease. There is a slight male predilection.
Pathology and pathophysiology
The pathogenesis of osteosarcoma is currently unknown, but it has been linked to the p-53 tumor suppressor gene. Familial cases are associated with retinoblastoma.
Grossly the tumor shows a glistening grey/white tissue with mineralization. There can be areas of necrosis with cystic degeneration. Microscopically the hallmark of diagnosis is the production of osteoid by malignant cell which can have varying morphology. Chondroblastic subtype osteosarcoma can have an appearance very similar to high grade chondroid tumors with lobular nests of cartilage produced by malignant stromal cells. The presence of a small portion of classic osteogenic sarcoma in a large chondroid lesion is sufficient to diagnose the tumor as osteosarcoma.
- Fracture Callus
- Ewing's sarcoma
- Aneurysmal Bone Cyst
- Giant Cell Tumor
- Fibrous Dysplasia
The etiology of osteosarcoma is not well understood. There is consensus that the cause is multifactorial, and includes environmental and genetic factors.
Radiographic and laboratory findings
X-ray findings are critical in the diagnosis of osteosarcoma, and are often enough to prompt a biopsy of the lesion. Characteristically the cancer causes an infiltrative destruction pattern and a periosteal reaction in which new bone is created perpendicularly to the cortex known as the sunburst appearance. One might also see codman’s triangle or new subperiosteal bone laid down between rapidly growing tumor and old periosteum. These findings are the result of the bodys attempt to contain the lesion as it grows.
CT scan will show a similar destructive lesion most often originating in the medulary canal with cortical destruction and a large soft tissue mass. There will be calcification in the interior of the lesion with less mineralization peripherally.
MRI will highlight the proximity to anatomic structures as well as the extent of the bone marrow involvement which will dictate the resection level of the lesion.
Bone scan and PET scan will show increased uptake of the radiotracers and will identify skeletal metastases.
Lab findings can be an elevated alkaline phosphatase but are non specific.
Risk factors and prevention
While there are no known prevention strategies for osteosarcoma, previous radiation therapy appears to be a risk factor.
The typical treatment for someone with osteosarcoma is pre-operative chemotherapy consisting of cisplatin and doxorubicin, surgery with the hopes of limb salvage, followed by post-operative chemotherapy. The most important prognostic factor is the percent of tumor necrosis caused by the pre-operative chemotherapy. Tumor necrosis of ninety percent or greater is associated with good survival while less necrosis is associated with poor outcomes.
Osteosarcoma does not respond to radiation therapy, and therefore has no role in treatment.
60-70 Percent of those with disease localized to an extremity have high cure rates. Complications include loss of limb, pathological fracture if untreated, and recurrence of disease often with metastasis. Survival is negatively impacted by spinopelvic location, very young or very old age at diagnosis, relatively low amount of tumour necrosis, lung metastasis and skeletal metastasis.
A multidisciplinary approach to patients with osteosarcoma will be most beneficial. The potential loss of a limb can be devastating news, and will require long-term adjustment.
Osteosarcoma, osteogenic sarcoma, sunburst, codman’s triangle, paget’s disease, pagetic sarcoma
Skills and competencies
A medical student should be able to recognize and describe the lesion radiographically.