High-grade surface osteosarcoma

Last revised by Joachim Feger on 19 Dec 2022

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

High-grade surface osteosarcomas are very rare and constitute <1% of all osteosarcomas. There seems to be a peak incidence in the 2nd and 3rd decade of life and a male preference 1-5.

The diagnosis of high-grade surface osteosarcomas is based on a combination of typical radiographic features with the histology of high-grade osteosarcoma.

Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:

  • imaging features of a bone tumor

  • histological finding of a high-grade osteosarcoma

  • origin from the surface of the bone

  • no significant intraosseous part

The most common complaints are swelling and pain 1. On rare occasions, there is joint stiffness or even no symptoms at all 3,4.

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 1-3.

The tumor has been found in the following locations 1-5:

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 1.

Microscopic features of high-grade surface osteosarcomas are those of conventional high-grade osteosarcoma 1.

Irrelevant for diagnosis 1.

General imaging features of high-grade surface osteosarcomas are the following 1,2,5:

  • 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 the main tumor and cortex

  • periosteal reaction uncommon

  • relatively high circumferential involvement (20-100%)

On plain radiographs high-grade surface osteosarcomas will usually display the following characteristics 1:

  • radiodense ill-defined

  • fluffy immature ossification

CT can demonstrate the following:

  • osteoid matrix

  • cortical erosions

  • cortical thickening

  • medullary involvement

MRI can 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

The radiological report should include a description of the following 1,6:

  • form, location and size

  • tumor margins and transition zone

  • circumferential extent

  • cortical erosion, cortical breakthrough

  • medullary components

  • soft tissue component

  • infiltration of neurovascular structures

Tumor management includes a combination of wide surgical excision and chemotherapy 2.

The five-year survival varies with different studies and ranges from roughly 40-80% 1-3. Localized disease and a good response to neoadjuvant good prognostic factors 1.

High-grade surface osteosarcoma was first described by the American orthopedic surgeon Kenneth C. Francis and his pathologist and surgeon colleagues Robert VP Hutter and Bradley L Coley in 1964 2,3,7.

Conditions that can mimic the presentation of high-grade surface osteosarcomas include 1,4:

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