How is a possible chordoma detected?
Chordoma tumors are typically detected through imaging tests, which show organs and other structures inside the body, including tumors. The way the tumor looks on imaging tests can tell a radiologist whether it might be chordoma.
When a chordoma is suspected, you will need magnetic resonance imaging, also called MRI, to help doctors make a diagnosis and plan for treatment. An MRI is the best way to see a chordoma and how it is affecting the tissue around it, such as muscles, nerves, and blood vessels. No matter where the tumor is located, an MRI of the entire spine should be performed to see if the tumor may have spread to or developed in other areas of the spine. Chordoma is best seen on an MRI with a setting called T2 weighted imaging.
Another imaging test called computed tomography, also called CT or CAT scan, is recommended in addition to MRI if it is not certain whether the tumor is chordoma. CT scans of the chest, abdomen, and pelvis are recommended to make sure there is no spread of tumor. Imaging tests should be interpreted by a radiologist who has experience diagnosing bone tumors.
In some cases doctors may order a positron emission tomography, or PET, scan. These are usually whole-body scans that look for widespread tumor activity. PET scans provide information about your body’s metabolic function; for cancer specifically, PET scans pick up on tumors that are rapidly using glucose (sugar). Cancer cells metabolize much more glucose than regular cells, so tumors “light up” on the scan. Because chordoma cells typically grow slowly, however, they are not always picked up as well by PET scans, so they are not widely used in diagnosing chordoma.
How is chordoma diagnosed?
Imaging tests can show the possibility of a chordoma, but a definitive diagnosis can only be made by a pathologist who examines a sample of tumor tissue under a microscope. For this reason, your medical team may consider taking a small sample of tissue from the tumor, called a biopsy, prior to surgery if the tumor can be reached safely (see important information below regarding biopsies).
Tissue samples should be evaluated by a pathologist who has experience diagnosing bone tumors. Your pathologist may test your tumor tissue for the presence of a protein called brachyury. Nearly all chordomas have high levels of brachyury, which makes it helpful for diagnosis.
For sacral and mobile spine tumors, a trocar CT-guided biopsy is recommended and should be done from the back. Trocar CT-guided biopsy uses a CT scan to precisely direct the biopsy needle to the correct location. The biopsy needle is enclosed in a tube to keep tumor cells from spreading along the path of the needle – this is often called seeding. Talk with your doctors to learn if they plan to use this method if a biopsy is recommended.
Skull base tumors can be difficult to reach safely for a biopsy, so your surgeon may opt for a biopsy during surgery. This means that a pathologist will be prepared to examine a sample of tumor tissue removed at the start of surgery and give an immediate diagnosis, and the surgical team will proceed with surgery based on that information.
If you have a biopsy before surgery, it is recommended that your surgeon take out the tissue around the area of the biopsy during surgery in order to remove any chordoma cells that might have spread when the biopsy disturbed the tumor.