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There are two ways in which oncologists classify the different types of osteosarcoma, the most common form of bone cancer. First, they must determine if the osteosarcoma is primary (occurring as a result of an abnormality in bone development) or secondary (occurring as a result of another condition). Primary osteosarcomas are more commonly diagnosed in children and teenagers whose bones are still growing, while secondary osteosarcomas often occur in adults whose bones are fully formed. Because secondary osteosarcomas are usually considered higher-grade malignancies than primary osteosarcomas, the treatment recommendations tend to be different for each.

There are 3 main types of primary osteosarcoma – intramedullary osteosarcoma, juxtacortical osteosarcoma, and extraskeletal osteosarcoma. They differ based on the bone cancer's location and appearance:

Intramedullary osteosarcoma

This type is the most common and accounts for nearly 80 percent of all osteosarcoma diagnoses. These bone cancers develop in the medullary cavity of a long bone, such as the femur. Additionally, there are a number of subtypes of intramedullary osteosarcoma, each based on the type of cells that make up the tumor. Common subtypes include osteoblastic, condroblastic, fibroblastic, small-cell and epithelioid.

Juxtacortical osteosarcoma

This type is the second most common and accounts for between 10 and 15 percent of all diagnoses. These bone cancers develop on the outer surface of the bones or the periosteum (the dense layer of connective tissue that covers the bones).

Extraskeletal osteosarcoma

This type is extremely rare, accounting for fewer than 5 percent of all diagnoses. These tumors arise in soft tissues and are not attached to bone; they often arise at a site of prior radiation therapy.

With any of these types of osteosarcoma, oncologists may also use the terms “synchronous” and “metachronous” to refer to osteosarcomas that involve more than one lesion in more than one bone. With synchronous osteosarcomas, these lesions are detected within a six month span; with metachronous osteosarcomas, the lesions are discovered more than six months apart.

Moffitt Cancer Center’s approach to osteosarcoma

At Moffitt Cancer Center, we have extensive experience in treating all types of osteosarcoma. We welcome adults and teenagers alike, and no referrals are required to make an appointment. To learn more, call 1-888-663-3488 or submit a new patient registration form online.