Osteosarcoma Types

There are several different subtypes of osteosarcoma that vary in where they arise, how they appear under the microscope, how aggressively they behave and, in some cases, how they are treated.

Osteosarcoma is the most common primary cancer of bone. It develops when malignant cells produce abnormal bone tissue, known as osteoid. All types of osteosarcomas share this defining feature.

At Moffitt Cancer Center, our multidisciplinary sarcoma team carefully evaluates each tumor to determine its specific subtype and develop an individualized treatment plan.

Primary Osteosarcoma

Primary osteosarcoma develops de novo, meaning it arises without a preexisting bone disorder. It most commonly affects children, adolescents and young adults, although it can occur at any age.

The most common subtype is conventional high-grade osteosarcoma, which develops within the center of the bone (intramedullary or central osteosarcoma). It most often occurs near the ends of long bones, particularly around the knee (distal femur and proximal tibia) and the proximal humerus. Under the microscope, conventional osteosarcoma may be described as osteoblastic, chondroblastic or fibroblastic depending on the predominant tissue produced by the tumor. These microscopic patterns generally do not change the standard treatment approach.

Less common primary osteosarcoma subtypes include:

• Telangiectatic osteosarcoma – A rare high-grade subtype containing blood-filled spaces that can resemble a benign bone cyst on imaging.
• Small-cell osteosarcoma – A rare high-grade subtype that may resemble Ewing sarcoma and requires specialized pathologic evaluation.
• Low-grade central osteosarcoma – An uncommon, slower-growing tumor that generally has a more favorable prognosis than conventional high-grade osteosarcoma.

Surface Osteosarcoma

Some osteosarcomas develop on the outer surface of the bone rather than within the marrow cavity. These are known as surface osteosarcomas and include:

• Parosteal osteosarcoma – Usually a low-grade tumor that arises from the outer surface of the bone. Surgery is often the primary treatment.
• Periosteal osteosarcoma – An intermediate-grade tumor that develops beneath the periosteum, the connective tissue blood supply covering the bone.
• High-grade surface osteosarcoma – A rare but aggressive subtype that is generally treated similarly to conventional high-grade osteosarcoma.

Secondary Osteosarcoma

Secondary osteosarcoma develops in bone that is abnormal from another cause. It occurs more commonly in older adults and may arise in association with conditions such as Paget disease of bone, avascular necrosis, infection or prior therapeutic radiation.

Extraskeletal Osteosarcoma

Extraskeletal osteosarcoma is a rare cancer that develops in soft tissues rather than bone. Although it also produces malignant osteoid, it is considered a distinct soft tissue sarcoma rather than a primary bone osteosarcoma. Some cases occur in areas that have previously received radiation therapy.

How Osteosarcoma Influences Treatment

Treatment recommendations depend on several factors, including:

• The specific osteosarcoma subtype
• Whether the tumor is low grade or high grade
• Whether the cancer is confined to its original location or has spread
• The size and location of the tumor
• Whether complete surgical removal is possible
• The patient’s age and overall health

Most patients with conventional high-grade osteosarcoma are treated with a combination of chemotherapy and surgery. In contrast, many low-grade osteosarcoma subtypes can be successfully treated with surgery alone.

Moffitt Cancer Center’s Approach to Osteosarcoma

Because osteosarcoma is rare, an accurate diagnosis by an experienced multidisciplinary team is essential. At Moffitt Cancer Center, orthopedic and surgical oncologists, medical oncologists, musculoskeletal radiologists and sarcoma pathologists work together to confirm each diagnosis and develop an individualized treatment plan.

Our team treats adults, children, adolescents and young adults with all types of osteosarcoma using the latest surgical techniques, systemic therapies and clinical trials when appropriate. No referral is required to schedule an appointment. To learn more, call 1-888-346-0201 or submit a new patient registration form online.