How Is Osteosarcoma Diagnosed?

If you have some of the symptoms of osteosarcoma, your doctor will begin your diagnosis with a medical history and physical exam.

• Medical history and physical examination - Your doctor will take a complete medical history by asking you about your risk factors, symptoms, and other health problems or concerns. The doctor will also do a physical exam to look for signs of osteosarcoma and other health problems.

A biopsy is the only way to tell for sure whether you have osteosarcoma. This involves cutting out a small piece of tissue and sending it to a laboratory. A pathologist (a doctor who specializes in diagnosing diseases) will look at the tissue under a microscope to see whether it has cancerous cells. This might be done by needle biopsy or open biopsy.

• Needle biopsy - A needle biopsy can be done with a thin (also known as fine) or thick needle. For osteosarcoma, the doctor will probably use a thick needle to take out a cylinder of tissue. Although fine needle biopsy is easier on the patient, it does not always collect enough cells and patients often need a second biopsy. The doctor may use a computed tomography (CT or CAT) scan to help guide the biopsy needle.
• Open biopsy - The surgeon cuts through the skin, finds the tumor, and cuts out a piece of tissue.
  

• Certain blood tests can be helpful in figuring how serious (advanced) the osteosarcoma is. Higher levels of the following chemicals in the blood mean that the cancer will be more difficult to cure:
  
• Alkaline phosphatase - Alkaline phosphatase may be elevated in osteosarcoma.
• Lactate dehydrogenase (LDH) - Patients without metastases who have a normal LDH level tend to do better than those with a high level.
• Imaging procedures allow doctors to learn where the cancer is located and whether it has spread from the original bone to other areas of the body. This can help determine which treatments will work best.
• Bone x-ray - A bone x-ray can give important information about bone lesions that could indicate osteosarcoma.
• Chest x-ray - A chest x-ray is used to find cancer that has spread (metastasized) to the lung if the metastasis is at least a half inch or larger.
• Computed tomography (CT or CAT) scan - Instead of taking one picture, like a conventional x-ray, a CT scanner takes many pictures as it rotates around you. A computer combines these pictures into an image of a slice of your body (like a loaf of sliced bread). A CT scan can show whether the tumor has grown into nearby tissue, such as muscle or fat. It can also help your doctor find the best spot to biopsy. In addition, CT scans are useful for finding out whether the tumor has spread to the lungs.
• Magnetic resonance imaging (MRI) - This procedure uses powerful magnets and radio waves to take detailed cross-sectional images. MRI produces images of cross-sectional slices of your body like a CT scanner. It can also make images of slices that are parallel to the length of your body. MRI provides detailed pictures of the soft tissues, bone tumor, and bone marrow cavity and some doctors think that MRI is better for evaluating osteosarcoma than a CT scan. MRI scans are also useful in finding metastases in the brain and spinal cord.
• Positron emission tomography (PET) - Cancer cells use glucose (sugar) more quickly than most other body organs. During a PET scan, the doctor injects a small amount of glucose that has a radioactive atom into your arm. A special camera in the PET machine can detect the radioactivity. This test is useful to see if the cancer has spread.
• Radionuclide bone scan - The doctor injects a radioactive dye into your vein. The tumor absorbs the radioactive material and a special camera detects it. A computer then creates a picture of all the bones in your body. The tumor looks like a dark spot on the picture, showing the area where most radioactivity has been absorbed. Radionuclide bone scans are used to find “skip” lesions (tumors that have spread from one site on a bone to another site on the same bone) and distant metastases. This test can be repeated after chemotherapy to show how responsive the tumor was to the chemotherapy drugs.