Central (Medullary) Tumors
Surface (Peripheral) Tumors

Osteosarcoma is a primary malignant tumor of the appendicular skeleton that is characterized by the direct formation of bone or osteoid tissue by the tumor cells. The World Health Organization’s histologic classification [1] of bone tumors separates the osteosarcomas into central (medullary) and surface (peripheral) [2,3] tumors and recognizes a number of subtypes within each group.

• Conventional central osteosarcomas.



• Telangiectatic osteosarcomas.



• Intraosseous well-differentiated (low-grade) osteosarcomas.



• Small cell osteosarcomas.

• Parosteal (juxtacortical) well-differentiated (low-grade) osteosarcomas.[4]



• Periosteal osteosarcoma: low-grade to intermediate-grade osteosarcomas.



• High-grade surface osteosarcomas.[3,5,6]

The most common pathologic subtype is conventional central osteosarcoma, which is characterized by areas of necrosis, atypical mitoses, and malignant osteoid tissue and/or cartilage. The other subtypes are much less common, each occurring at a frequency of less than 5%. Telangiectatic osteosarcoma may be confused radiographically with an aneurysmal bone cyst or giant cell tumor. This variant should be approached as a conventional osteosarcoma.[7,8] Recognition of intraosseous well-differentiated osteosarcoma and parosteal osteosarcoma is important because these are associated with the most favorable prognosis and can be treated successfully with radical excision of the primary tumor alone.[4] Periosteal osteosarcoma has a generally good prognosis [9,10] and treatment is guided by histologic grade.[11]

Malignant fibrous histiocytoma (MFH) of bone is treated according to osteosarcoma treatment protocols. MFH should be distinguished from angiomatoid fibrous histiocytoma, a low-grade tumor that is usually noninvasive, small, and associated with an excellent outcome with surgery alone.[12] One study suggests similar event-free survival rates for MFH and osteosarcoma.[13]

Extraosseous osteosarcoma is a malignant mesenchymal neoplasm without direct attachment to the skeletal system. Previously, treatment for extraosseous osteosarcoma followed soft tissue sarcoma guidelines,[14] though a retrospective analysis of the German Cooperative Osteosarcoma Study identified a favorable outcome for extraosseous osteosarcoma treated with surgery and conventional osteosarcoma therapy.[15]

References

1. Schajowicz F, Sissons HA, Sobin LH: The World Health Organization's histologic classification of bone tumors. A commentary on the second edition. Cancer 75 (5): 1208-14, 1995.  [PUBMED Abstract]
   
   
2. Antonescu CR, Huvos AG: Low-grade osteogenic sarcoma arising in medullary and surface osseous locations. Am J Clin Pathol 114 (Suppl): S90-103, 2000.  [PUBMED Abstract]
   
   
3. Kaste SC, Fuller CE, Saharia A, et al.: Pediatric surface osteosarcoma: clinical, pathologic, and radiologic features. Pediatr Blood Cancer 47 (2): 152-62, 2006.  [PUBMED Abstract]
   
   
4. Hoshi M, Matsumoto S, Manabe J, et al.: Oncologic outcome of parosteal osteosarcoma. Int J Clin Oncol 11 (2): 120-6, 2006.  [PUBMED Abstract]
   
   
5. Okada K, Unni KK, Swee RG, et al.: High grade surface osteosarcoma: a clinicopathologic study of 46 cases. Cancer 85 (5): 1044-54, 1999.  [PUBMED Abstract]
   
   
6. Staals EL, Bacchini P, Bertoni F: High-grade surface osteosarcoma: a review of 25 cases from the Rizzoli Institute. Cancer 112 (7): 1592-9, 2008.  [PUBMED Abstract]
   
   
7. Bacci G, Ferrari S, Ruggieri P, et al.: Telangiectatic osteosarcoma of the extremity: neoadjuvant chemotherapy in 24 cases. Acta Orthop Scand 72 (2): 167-72, 2001.  [PUBMED Abstract]
   
   
8. Weiss A, Khoury JD, Hoffer FA, et al.: Telangiectatic osteosarcoma: the St. Jude Children's Research Hospital's experience. Cancer 109 (8): 1627-37, 2007.  [PUBMED Abstract]
   
   
9. Unni KK, Dahlin DC, Beabout JW: Periosteal osteogenic sarcoma. Cancer 37 (5): 2476-85, 1976.  [PUBMED Abstract]
   
   
10. Rose PS, Dickey ID, Wenger DE, et al.: Periosteal osteosarcoma: long-term outcome and risk of late recurrence. Clin Orthop Relat Res 453: 314-7, 2006.  [PUBMED Abstract]
    
    
11. Grimer RJ, Bielack S, Flege S, et al.: Periosteal osteosarcoma--a European review of outcome. Eur J Cancer 41 (18): 2806-11, 2005.  [PUBMED Abstract]
    
    
12. Daw NC, Billups CA, Pappo AS, et al.: Malignant fibrous histiocytoma and other fibrohistiocytic tumors in pediatric patients: the St. Jude Children's Research Hospital experience. Cancer 97 (11): 2839-47, 2003.  [PUBMED Abstract]
    
    
13. Picci P, Bacci G, Ferrari S, et al.: Neoadjuvant chemotherapy in malignant fibrous histiocytoma of bone and in osteosarcoma located in the extremities: analogies and differences between the two tumors. Ann Oncol 8 (11): 1107-15, 1997.  [PUBMED Abstract]
    
    
14. Wodowski K, Hill DA, Pappo AS, et al.: A chemosensitive pediatric extraosseous osteosarcoma: case report and review of the literature. J Pediatr Hematol Oncol 25 (1): 73-7, 2003.  [PUBMED Abstract]
    
    
15. Goldstein-Jackson SY, Gosheger G, Delling G, et al.: Extraskeletal osteosarcoma has a favourable prognosis when treated like conventional osteosarcoma. J Cancer Res Clin Oncol 131 (8): 520-6, 2005.  [PUBMED Abstract]
    
    

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