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Osteosarcoma is a high-grade malignant bone-forming tumor characterized by production of osteoid by malignant mesenchymal cells.

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https://www.youtube.com/watch?v=xOsovd6vzdE

https://www.youtube.com/watch?v=XEezTvqsNCU

CLASSIFICATION

Histological classification Morphological classification Etiological classification
Conventional os. Parosteal os. Primary os.
Telangiectatic os. Periosteal os. Secondary os.
Small cell os. High-grade surface os.

WHO Classification

![Updated classification of human malignant, bone mass-depositing osteosarcoma considering the latest WHO 2020 guidelines for bone tumors. The picture outlines the location of tumors (note that it can be central or in the surface of the bone, or intramedullary in the bone marrow medulla) and associated molecular and clinical features. Compiled from revision of literature from [34,37,38]. MDM2— human homolog of mouse double minute 2; CDK4—cyclin-dependent kinase 4. Created with BioRender.com (figure created on 13 March 2023).

Martins-Neves SR, Sampaio-Ribeiro G, Gomes CMF. Self-Renewal and Pluripotency in Osteosarcoma Stem Cells’ Chemoresistance: Notch, Hedgehog, and Wnt/β-Catenin Interplay with Embryonic Markers. International Journal of Molecular Sciences. 2023; 24(9):8401. https://doi.org/10.3390/ijms24098401](attachment:0f395a94-4892-4166-a4e2-533b9ac888c9:ijms-24-08401-g001.png)

Updated classification of human malignant, bone mass-depositing osteosarcoma considering the latest WHO 2020 guidelines for bone tumors. The picture outlines the location of tumors (note that it can be central or in the surface of the bone, or intramedullary in the bone marrow medulla) and associated molecular and clinical features. Compiled from revision of literature from [34,37,38]. MDM2— human homolog of mouse double minute 2; CDK4—cyclin-dependent kinase 4. Created with BioRender.com (figure created on 13 March 2023).

Martins-Neves SR, Sampaio-Ribeiro G, Gomes CMF. Self-Renewal and Pluripotency in Osteosarcoma Stem Cells’ Chemoresistance: Notch, Hedgehog, and Wnt/β-Catenin Interplay with Embryonic Markers. International Journal of Molecular Sciences. 2023; 24(9):8401. https://doi.org/10.3390/ijms24098401

Etiological classification

Type Age Description
Primary (de novo) 10-25 years Most common (75%)
Secondary > 40 years Post-radiation, Paget’s disease, osteogenesis imperfecta, fibrous dysplasia

Secondary osteosarcoma:

Malignant degeneration of benign entities Germline abnormalities
‣ ‣
Large bone infarction ‣
Post-radiotherapy ‣

Clinical Features

Epidemiology:

Feature Description
Incidence ~20% of all primary bone tumors
Age 10–25 years (primary peak); second smaller peak >40 years (often secondary)
Sex Male > Female (1.5–2:1)