How is osteosarcoma diagnosed?
Osteosarcomas are usually found when a person goes to the doctor because of signs or symptoms they are having. If a bone tumor is suspected, tests will be needed to find out for sure.
Medical history and physical exam
If a person has signs or symptoms that suggest a tumor in or around a bone, the doctor will want to take a complete medical history to find out more about the symptoms. A physical exam can provide information about a possible tumor, as well as other health problems. For example, the doctor may be able to see or feel an abnormal mass.
The doctor may also look for problems in other parts of the body. When people (especially adults) do have cancer in the bones, it’s often the result of cancer that started somewhere else and then spread to the bones.
If the doctor suspects a person could have osteosarcoma (or another type of bone tumor), more tests will be done. These might include imaging tests, biopsies, and/or lab tests.
Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of the body. Imaging tests may be done for a number of reasons, including:
- To help find out if a suspicious area might be cancer
- To help determine if a cancer may have started in another part of the body
- To learn how far cancer has spread
- To help determine if treatment is working
- To look for signs that the cancer may have come back
Patients who have or may have osteosarcoma will have one or more of these tests.
This is often the first test done if a doctor suspects a bone tumor. Doctors can often recognize a bone tumor such as osteosarcoma based on plain x-rays of the bone. But other imaging tests might be needed as well.
Even if results of an x-ray strongly suggest a person has osteosarcoma, a biopsy will still be needed to confirm that it is cancer rather than some other problem, such as an infection.
Magnetic resonance imaging (MRI) scan
MRI scans provide detailed images of soft tissues in the body. These scans make detailed images using radio waves and strong magnets instead of x-rays, so no radiation is involved. A contrast material called gadolinium may be injected into a vein before the scan to better see details.
Often, an MRI scan is done to get a more detailed look at a bone mass seen on an x-ray. MRI scans can usually show if the mass is likely to be a tumor, an infection, or some type of bone damage from other causes. MRI scans can also help show the exact extent of a tumor, as they provide a detailed view of the marrow inside bones and the soft tissues around the tumor. Sometimes, the MRI can help find small bone tumors several inches away from the main tumor (called skip metastases). Knowing the extent of an osteosarcoma is very important when planning surgery. An MRI scan usually gives better details than a CT scan (described below).
An MRI scan can take up to an hour. You (or your child) may have to lie on a table that slides inside a narrow tube, which is confining and can be distressing. Newer, more open MRI machines can help with these feelings, but the test still requires staying still for long periods of time. The machines also make buzzing and clicking noises that may be disturbing. Sometimes, younger children are given medicine to help keep them calm or even asleep during the test.
Computed tomography (CT) scan
The CT scan uses x-rays to make detailed cross-sectional images of parts of the body. If a bone x-ray shows a tumor, CT scans are sometimes used to see if the tumor has grown into nearby muscle, fat, or tendons, although MRI is often better for this. A CT scan of the chest is often done to look for spread of the cancer to the lungs. CT scans may also be done to look for the spread of the cancer to other parts of the body.
Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around a person lying on a table. A computer then combines these pictures into detailed images of slices of the part of the body being studied.
Before the test, you (or your child) may be asked to drink a contrast solution and/or get an intravenous (IV) injection of a contrast dye that helps better outline abnormal areas in the body. If the contrast dye is to be injected, you (or your child) may need an IV line. The contrast may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if you (or your child) have any allergies or have ever had a reaction to any contrast material used for x-rays.
A CT scanner has been described as a large donut, with a narrow table in the middle opening. During the test, the table slides in and out of the scanner. You (or your child) will need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken. In some cases, children may need to be sedated before the test to stay still and help make sure the pictures come out well.
This test is sometimes done to see if cancer has spread to the lungs. It can find larger tumors, but it is not as good as a CT scan for spotting smaller tumors. If a CT scan of the chest is done, a chest x-ray probably won’t be needed.
A bone scan can help show if a cancer has spread to other bones, and is often part of the workup for people with osteosarcoma. This test is useful because it can show the entire skeleton at once. (A positron emission tomography [PET] scan, described below, can often provide similar information, so a bone scan might not be needed if a PET scan is done.)
For this test, a small amount of low-level radioactive material is injected into a vein (intravenously, or IV). (The amount of radioactivity used is very low and will pass out of the body within a day or so.) The substance settles in areas of damaged bone throughout the entire skeleton over the course of a couple of hours. You (or your child) then lie on a table for about 30 minutes while a special camera detects the radioactivity and creates a picture of the skeleton. Younger children may be given medicine to help keep them calm or even asleep during the test.
Areas of active bone changes appear as “hot spots” on the skeleton because they attract the radioactivity. Hot spots may suggest areas of cancer, but other bone diseases can also cause the same pattern. To make an accurate diagnosis, other tests such as plain x-rays, MRI scans, or even a bone biopsy might be needed.
Positron emission tomography (PET) scan
For a PET scan, a form of radioactive sugar (known as FDG) is injected into the blood. The amount of radioactivity used is very low and will pass out of the body within a day or so. Because cancer cells in the body are growing quickly, they absorb large amounts of the sugar. After about an hour, you (or your child) will lie on a table in the PET scanner for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body. The picture is not detailed like a CT or MRI scan, but it provides useful information about the whole body.
PET scans can help show the spread of osteosarcomas to the lungs, other bones, or other parts of the body, and can also help in following the response to treatment.
Some newer machines can do a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT scan.
To learn more about this and other imaging tests, see our document Imaging (Radiology) Tests.
The results of imaging tests might strongly suggest that a person has some type of bone cancer, but a biopsy (removing some of the tumor for viewing under a microscope and other lab testing) is the only way to be certain. A biopsy is also the best way to tell osteosarcoma from other types of bone cancer.
If the tumor is in a bone, it is very important that a surgeon experienced in treating bone tumors does the biopsy. Whenever possible, the biopsy and surgical treatment should be planned together, and the same orthopedic surgeon should do both the biopsy and the surgery. Proper planning of the biopsy can help prevent later complications and might reduce the amount of surgery needed later on.
There are 2 main types of biopsies.
For these biopsies, the doctor uses a hollow needle to remove a small sample of the tumor. The biopsy is usually done with local anesthesia, where numbing medicine is injected into the skin and other tissues over the biopsy site. In some cases, sedation or general anesthesia (where the patient is asleep) may be needed.
Often, the doctor can aim the needle by feeling the suspicious area if it is near the surface of the body. If the tumor can’t be felt because it is too deep, the doctor can guide the needle into the tumor while viewing a CT scan. This is called a CT guided needle biopsy.
Core needle biopsy: In a core needle biopsy, the doctor uses a large, hollow needle to remove a small cylinder of tissue from the tumor.
Fine needle aspiration (FNA) biopsy: For an FNA biopsy, the doctor uses a very thin needle attached to a syringe to withdraw (aspirate) a small amount of fluid and some cells from the tumor. This type of biopsy is rarely used for bone tumors.
Surgical (open) biopsy
In an open biopsy, the surgeon cuts through the skin, exposes the tumor, and then cuts out a piece of it. These biopsies are usually done with the patient under general anesthesia (in a deep sleep). They can also be done using a nerve block, which numbs a large area.
This type of biopsy must be done by an expert in bone tumors, or it could result in problems later on. For example, if the tumor is on the arm or leg, it’s possible the chance for saving the limb may be lost. If possible, the incision in the skin used in the biopsy should be lengthwise along the arm or leg because this is the way the incision will be made during the operation to remove the cancer. The entire scar of the original biopsy will also have to be removed, so making the biopsy incision this way lessens the amount of tissue that needs to be removed later on.
Testing the biopsy samples
All samples removed by biopsy are sent to a pathologist (a doctor specializing in lab tests) to be looked at under a microscope. Tests looking for chromosome or gene changes in the tumor cells may also be done. These tests can help tell osteosarcoma from other cancers that look like it under the microscope, and they can sometimes help predict whether the osteosarcoma is likely to respond to therapy.
If osteosarcoma is diagnosed, the pathologist will assign it a grade, which is a measure of how quickly the cancer is likely to grow and spread, based on how it looks under a microscope. Cancers that look somewhat like normal bone tissue are described as low grade, while those that look very abnormal are called high grade. For more on grading, see the section “How is osteosarcoma staged?”
Blood tests are not needed to diagnose osteosarcoma, but they may be helpful once a diagnosis is made. For example, high levels of chemicals in the blood such as alkaline phosphatase and lactate dehydrogenase (LDH) can suggest that the osteosarcoma may be more advanced than it appears.
Other tests such as blood cell counts and blood chemistry tests are done before surgery and other treatments to get a sense of a person’s overall health. These tests are also used to monitor a person’s health while they are getting chemotherapy.
Last Medical Review: 04/18/2014
Last Revised: 04/18/2014