After osteosarcoma or malignant fibrous histiocytoma (MFH) has been diagnosed, tests are done to find out if cancer cells have spread to other parts of the body.

The process used to find out if cancer has spread to other parts of the body is called staging. For osteosarcoma and malignant fibrous histiocytoma (MFH), most patients are grouped according to whether cancer is found in only one part of the body or has spread. The following tests and procedures may be used:

• X-ray : An x-ray of the organs and bones inside the body. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body. X-rays will be taken of the chest and the area where the tumor formed.

• CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography. Pictures will be taken of the chest and the area where the tumor formed.

• MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).

• Bone scan : A procedure to check if there are rapidly dividing cells, such as cancer cells, in the bone. A very small amount of radioactive material is injected into a vein and travels through the bloodstream. The radioactive material collects in the bones and is detected by a scanner.

• PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.

There are three ways that cancer spreads in the body.

The three ways that cancer spreads in the body are:

• Through tissue. Cancer invades the surrounding normal tissue.
• Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
• Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.

When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if bone cancer spreads to the lung, the cancer cells in the lung are actually bone cancer cells. The disease is metastatic bone cancer, not lung cancer.

Osteosarcoma and MFH are described as either localized or metastatic.

• Localized osteosarcoma or MFH has not spread out of the bone where the cancer started. There may be one or more areas of cancer in the bone that can be removed during surgery.
• Metastatic osteosarcoma or MFH has spread from the bone in which the cancer began to other parts of the body. The cancer most often spreads to the lungs. It may also spread to other bones.