There are two ways in which oncologists classify the different types of osteosarcoma. 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.
From there, oncologists must determine which of the following types an osteosarcoma should be classified as based on its location and appearance:
- Intramedullary osteosarcoma – This type is the most common and accounts for nearly 80 percent of all osteosarcoma diagnoses. These osteosarcomas 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 osteosarcomas 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.
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.