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| Parosteal Osteosarcoma |
| Etiology •Patients with mutations in the retinoblastoma gene have a several hundred fold greater incidence of osteosarcoma. |
| Pathogenesis •As with most malignancies, the precise pathogenesis is unclear. •The disease is associated with mutations in the retinoblastoma (Rb) gene, and deletions of or mutations in the p53 gene. •Other conditions that are associated with high bone turnover, such as Paget's disease and fibrous dysplasia of bone predispose to the development of osteosarcoma. •The tumor commonly arises during the time of maximal bone growth (late adolescence)., |
| Epidemiology •Most common primary malignant tumor of bone. •More commonly seen in men (about 2:1). |
| General Gross Description •Arise from the metaphysis of long bones. •Often big, bulky tumors. •Tan-white and gritty with areas of necrosis, hemorrhage and cystic degeneration. •The tumor frequently grows through the cortical bone and raises the periosteum. •The triangular space thus generated between the raised periosteum and the edge of the bone can be seen radiographically. •This triangle is often referred to as the Codman's triangle. |
| General Microscopic Description •The histological feature pathognomonic of osteosarcoma is the production of neoplastic osteoid matrix. •Tumor cells are osteocytes or osteoblasts and resemble normal osteoblasts. However, bizarre cells and atypia are invariably seen. •Other types of matrices, such as cartilage, are frequently seen. |
| Clinical Correlation •Most frequently arise near the knee joint; second most frequently near the hip joint. •Diseases that increase bone remodeling, such as Paget's disease, increase frequency of this malignancy. •Other "benign" tumors of bone and fibrous dysplasia also may dispose to osteosarcoma. •Osteosarcomas typically present as painful enlarging lesions. •In some cases, fracture of a bone on relatively minor trauma may be the first symptom of osteosarcoma. •As is true of most sarcomas, osteosarcoma spreads predominantly by the blood stream. •Approximately 20% of patients have pulmonary metastases at the time of diagnosis. •Current long-term survival (five year survival rates) are in the range of 60%. |
| References • Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th edition. Philadelphia, W.B. Saunders, 1994, pp. 1234. |
| Parosteal Osteosarcoma |
| Synopsis by: T.V.Rajan, M.D. Ph.D. (T1X500M91903)[70] |
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