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High-Grade Surface Osteosarcoma

High-grade surface osteosarcoma is a high-grade malignant bone-forming neoplasm arising on the surface of the bone.

Symptoms & Causes

Introduction

High-grade surface osteosarcoma is a malignant bone tumor that arises on the surface of bones and is characterized by high-grade osteoblastic activity.

Reference
WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours [Internet]. Lyon (France): International Agency for Research on Cancer; 2020 [cited 2024 09 11]. (WHO classification of tumours series, 5th ed.; vol. 3). Available from: https://tumourclassification.iarc.who.int/chapters/33.

Related Terminology
None

Subtype(s)
None

Localization

The three most common sites, in descending frequency, are the femur, tibia, and humerus. In the long bones, high-grade surface osteosarcomas are most frequently diaphyseal or diametaphyseal.

Symptoms

Swelling and pain of short duration are usual.

Epidemiology

High-grade surface osteosarcomas account for < 1% of osteosarcomas. The published incidence shows a male predominance and a peak incidence in the second decade of life. However, because there are very few published cases and most of them are derived from consultation files, the statistical significance is questionable.

Etiology

Unknown

Diagnosis & Treatment

Staging

The Union for International Cancer Control (UICC) TNM classification of malignant tumors does not recommend that the TNM staging system for bone tumors be applied to surface/juxtacortical osteosarcoma or juxtacortical chondrosarcoma. However, other staging systems, such as the American Joint Committee on Cancer (AJCC) TNM system, do include these tumors in the bone staging system. See also the information on staging in section Bone tumors: Introduction.

Pathogenesis

The pathogenetic mechanisms of high-grade surface osteosarcoma are unknown. High-grade surface osteosarcomas arising in parosteal osteosarcomas (dedifferentiated parosteal osteosarcomas) display amplification of MDM2 and CDK4. The single case of TSPAN31 (SAS) amplification in a high-grade surface osteosarcoma described was an example of dedifferentiated parosteal osteosarcoma because it had grade 1 foci.

Macroscopic Appearance

The tumor is usually well circumscribed externally and situated on the fibrous periosteal surface. It often extends through the periosteum to attach to or even erode the underlying cortical surface. Endosteal extension may be present, but the bulk of the tumor is outside the bone. Its cut surface is variable because its appearance depends on the predominant type of extracellular matrix produced, as well as on the cellularity of the tumor stroma.

Histopathology

These tumors are histologically identical to high-grade conventional osteosarcoma, with the same degree of matrix variability. Immunohistochemistry is not relevant to making the diagnosis.

Cytology

Not clinically relevant

Prognosis and Prediction

The overall 5-year survival rate of patients with high-grade surface osteosarcoma, compiled from the two studies reporting follow-up, is 62%. Factors that favor survival include good response to neoadjuvant chemotherapy and localized disease. Poor response to chemotherapy, metastatic disease at the time of presentation, and local recurrence are adverse factors. The presence of medullary involvement does not seem to be an independent prognostic factor.

Clinical Features

Diagnostic Molecular Pathology

Not clinically relevant

Essential and Desirable Diagnostic Criteria

Essential: bone tumor with compatible imaging; histologically high-grade osteosarcoma; arising on the surface of the bone without a substantial intraosseous component.

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