High-grade surface osteosarcoma

High-grade surface osteosarcomas are very rare and high-grade malignant osteoid forming tumors emerging from the bony surfaces similar to parosteal and periosteal osteosarcomas.

Epidemiology

High-grade surface osteosarcomas are very rare and constitute <1% of all osteosarcomas. There seems to be a peak incidence in the 2 and 3 decade of life and a male predilection .

Clinical presentation

Most common complaints are swelling and pain . On rare occasions, there is joint stiffness or even no symptoms at all .

Pathology

High-grade surface osteosarcomas are highly malignant osteosarcomas growing from the fibrous periosteal surfaces and are one of the three subtypes of surface osteosarcoma together with parosteal osteosarcoma and periosteal osteosarcoma .

Location

The tumor has been found in the following locations :

  • diaphyseal and diametaphyseal areas of long bones
  • femur
  • tibia
  • humerus
Macroscopic appearance

Macroscopically high-grade surface osteosarcomas are of variable appearance mostly dependent on the type of generated extracellular matrix. The bulk of the tumor is usually located outside of the bone with infiltration and extension of the periosteum inwards and erosion of the underlying cortex .

Microscopic appearance

Microscopic features of high-grade surface osteosarcomas are those of a conventional high-grade osteosarcoma .

Immunohistochemistry

Irrelevant for diagnosis .

Radiographic features

General imaging features of high-grade surface osteosarcomas are the following :

  • the tumor arises from the bony surfaces
  • dense ossifications
  • cortical erosions (≈ 50% of the cases)
  • medullary involvement (≈ 50% of the cases)
  • usually no cleavage plane between main tumor and cortex
  • periosteal reaction uncommon
  • relatively high circumferential involvement (20-100%)
Plain radiograph

On plain radiographs high-grade surface osteosarcomas will usually display the following characteristics :

  • radiodense ill-defined
  • fluffy immature ossification
CT

CT can demonstrate the following:

  • osteoid matrix
  • cortical erosions
  • cortical thickening
  • medullary involvement
MRI

MRI is able to accurately depict soft tissue and medullary involvement of high-grade surface osteosarcomas as well as peritumoral and/or medullary edema.

  • T1
    • osteoid matrix: low signal intensity
    • non-ossified soft tissue components: intermediate signal intensity
  • T2
    • osteoid matrix: low signal intensity
    • non-ossified soft tissue components: high signal intensity
  • T1 C+ (Gd): marked enhancement

Radiology report

The radiological report should include a description of the following :

  • form, location and size
  • tumor margins and transition zone
  • circumferential extent
  • cortical erosion, cortical breakthrough
  • medullary components
  • soft tissue component
  • infiltration of neurovascular structures

Treatment and prognosis

Tumor management includes a combination of wide surgical excision and chemotherapy .

The five-year survival varies with different studies and ranges from roughly 40-80% . Localized disease and a good response to neoadjuvant good prognostic factors .

History and etymology

High-grade surface osteosarcoma was apparently first described in 1964 by Francis .

Differential diagnosis

Conditions which can mimic the presentation of high-grade surface osteosarcomas include :

See also