Osteosarcoma is an aggressive, malignant bone-forming mesenchymal tumour, predominantly affecting the long bones (particularly distal femur, proximal tibia, and proximal humerus) of adolescents and young adults. Pain with or without a palpable mass is the most frequent clinical symptom
Fletcher CDM, Unni KK, Mertens F (Eds.)
. It may metastasize to other anatomic sites, particularly the lungs.
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone.
IARC Press: Lyon 2002
> Conventional osteosarcoma
Conventional osteosarcoma is the most common non-haematopoietic primary malignant tumour of bone, with an incidence rate of 4-5 cases /million population/year). Males are more frequently affected (M/F ratio 3:2). Aggressive local growth and rapid haematogenous systemic dissemination are typical features. Multidisciplinary therapy has made the prognosis somewhat more favourable.
Conventional osteosarcoma is a primary intramedullary malignant tumour in which the neoplastic cells produce osteoid. Most are mixed lytic/blastic lesions accompanied by cortical destruction and tumour extension into soft tissue. Histologically, tumours tend to be highly anaplastic and pleomorphic. Depending on the type of matrix produced, three major subtypes have been defined:
- Osteoblastic osteosarcoma
- Chondroblastic osteosarcoma
- Fibroblastic osteosarcoma
> Secondary osteosarcomas