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Osteogenic Sarcoma

 

 

Pathology

Histology shows:

  • Osteoid material
  • Anaplastic stromal cells

Characterized by the direct formation of bone or osteoid tissue by the tumor cells.

There are 3 categories of classic OS based on the predominant differentiation of the tumor cells.

 

Classification of Osteogenic Sarcoma by histology:

Classic

Osteoblastic

  • 50% cases
  • Abundant production of osteoid

 

Chrondroblastic

  • 25%
  • Differentiation towards cartilage

 

Fibroblastic

  • Spindle cell stroma with "herring bone" pattern similar to fibrosarcoma

 
Telangiectatic
  • 3% of all osteosarcomas
  • Radiolucent lesion and little new bone formation (radiology like aneurysmal bone cyst or giant cell tumor)
  • Cystic tumors
  • Path - blood filled dilated spaces
  • Viable tumor on periphery

 
Small cell
  • Histologically similar to Ewing sarcoma but produces malignant osteoid matrix

 

 

 

Classification by Location of Osteogenic Sarcoma:

Central (Medullary) Tumors
  • Conventional central "classic" osteosarcoma

 
  • Telangiectatic osteosarcoma

 
  • Intraosseous well-differentiated (low-grade) osteosarcoma

 
  • Small cell osteosarcoma

 
Surface (Peripheral) Tumors

Parosteal OS:

  • juxtacortical
  • well- differentiated (low-grade) OS
  • Less than 5% of all osteosarcomas
  • Older patients
  • Long history of symptoms
  • Arises from bone cortex (from a broad base) and no invasion of medullary cavity
  • Low grade with intense ossification
  • Indolent - low risk of distant metastatic disease
  • Good prognosis after radical excision
  • De-differentiation can occur

 

Periosteal OS:

  • low-grade to intermediate-grade OS
  • Arises on bone surface and no invasion of medullary cavity
  • Often arises on upper tibial metaphysis
  • Path - usually high grade chondroblastic OS
  • Worse prognosis than parosteal with greater chance of systemic spread
  • Treatment is guided by histologic grade

 

  • High-grade surface osteosarcoma

 

 

Conventional "classic" central osteosarcoma is the most common pathologic subtype.

Characterized by:

  • Areas of necrosis
  • Atypical mitoses
  • Malignant osteoid tissue and/or cartilage.

 

Below is a histopathology slide of osteogenic sarcoma. The pink material is osteoid. All of the malignant stromal cells are viable. This tumor is untreated.

 

In the past tumors were assigned a histologic grade I-IV based on the degree of nuclear anaplasia, but more recently tumors are stratified into low and high grade lesions.

To date immunoperoxidase techniques have contributed little to the diagnosis of this tumor, although some reports suggest that the identification of ‘osteocalcin’ and ‘osteonectin’ can help to distinguish osteoid from collagen [Fanburg JC et al. Osteocalcin and osteonectin immunoreactivity in the diagnosis of osteosarcoma. Am J Clin Path, 108,464-73].

The other subtypes are much less common, each occurring at a frequency of less than 5%.

Recognition of intraosseous well-differentiated osteosarcoma and parosteal osteosarcoma is important:

  • These are associated with the most favorable prognosis
  • Can be treated successfully with radical excision of the primary tumor alone.

 

Related tumors include fibrosarcoma and chondrosarcoma. These also arise from primitive mesenchyme capable of differentiating into fibrous tissue, cartilage or bone.

 

External Link:

Osteogenic sarcoma at the Atlas of Genetics and Cytogenetics in Oncology and Haematology

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