Osteosarcoma (also known as osteogenic sarcoma) is a malignant bone tumor found primarily in adolescents and young adults. It is an aggressive form of cancer and is found in the femur (thigh bone), tibia (shin bone), hip, shoulder and pelvis. It is the eighth most common form of cancer found in children and makes up approximately 20 percent of all primary bone cancers. In the United States, approximately 900 people each year are diagnosed with osteosarcoma.
While it most commonly affects children under the age of 18, osteosarcoma also can be seen in patients up to the age of 30. A smaller group of patients may develop this disease later in life, frequently secondary to radiation or other predisposing condition. Males are slightly more likely than females to have this tumor. Without treatment, osteosarcoma is universally fatal. However, with advances in chemotherapy and surgical techniques, the prognosis has improved drastically. With modern treatment protocols, most patients with localized osteosarcoma are expected to survive the condition with a functional limb.
The bone is a complex organ, which can be divided into three sections:
- Epiphysis – Found on the end of the bone, where spongy cancellous tissue is covered by the articular cartilage
- Metaphysis – Area that contains the growth plate, responsible for rapid increase in length during childhood and adolescence
- Diaphysis – Long part of the bone consisting of a strong outer tube (cortex) for support, and a soft interior, composed largely of bone marrow
The bones are among the most resilient parts of the human body. The entire skeletal structure maintains the shape of the body, protects vital organs and produces blood cells vital to nutrition.
Depending on the severity and level of osteosarcoma, the symptoms for each person will vary. Keep in mind that everyone’s body is different and will react somewhat differently to the cancer. The following are common osteosarcoma symptoms:
- A mass near the site of the cancer-infected area
- Decreased mobility in the joints around the affected area
- Increased pain at night
- Weakened bone structure
- Unexplained bone fractures
It is not uncommon for symptoms to be present for a few weeks, or even months, before diagnosis is made, simply because the symptoms of osteosarcoma are so closely related to other bone diseases. Consult a doctor to determine if you have osteosarcoma so testing and treatment can begin quickly.
There is little known about what causes osteosarcoma. However, there are several risk factors associated with this malignant tumor:
- Rapid bone growth – Since osteosarcoma commonly presents in patients around the time of rapid growth during adolescence, some have speculated a potentially causative effect. This is supported by a small amount of data to suggest that the disease is more common in taller individuals.
- Genetics – Another major factor is the genetic makeup of the person who has osteosarcoma. Genetic conditions such as Li-Fraumeni syndrome or retinoblastoma significantly increase the risk for developing this tumor.
- Paget’s disease – This condition has been strongly linked to formation of osteosarcoma in older patients.
- Previous radiation – For patients who have been exposed to high doses of radiation, the risk of contracting this tumor increases.
Osteosarcoma can be divided into two main forms:
- Localized – When osteosarcoma is localized, it means that it has remained singular to the bone where it started. Patients with localized osteosarcoma are advised to have chemotherapy done to help decrease the risk of the cancer spreading to other body parts.
- Metastatic – When the osteosarcoma has metastasized, the cancer has spread to areas beyond the originally affected bone. The most common place for this cancer to spread is the lungs. For these patients, surgery is performed to try to remove the metastases. Chemotherapy is administered to help reduce the risk of recurrence or to address anything missed during the surgical procedure.
Osteosarcoma can be categorized based upon various factors:
- Location – Most commonly, osteosarcoma originates within the metaphysis. When starting inside the bone, it is referred to as central osteosarcoma. On occasion, the tumor may arise on the surface of the bone, in which case it is called a surface (or juxtacortical) osteosarcoma. Rarely, osteosarcoma may arise entirely separate from a bone, an extra-skeletal (or soft tissue) osteosarcoma.
- Grade – Most malignant tumors are assigned a grade, based upon how aggressive they appear under the microscope. A classic osteosarcoma is high-grade, indicating a highly aggressive and malignant nature. Variants that are low- or intermediate-grade exist, which may help determine the necessary management.
- Appearance – When seen under the microscope, an osteosarcoma can be categorized by the appearance of the cells that comprise the tumor. These variants include osteoblastic, chondroblastic, telangiectatic, small cell, giant cell-rich and others.