Diagnosis and Grading
The main goal at the Siteman Cancer Center is to get an accurate diagnosis of your condition and decide what treatment is needed. Many brain tumors are benign and may only need vigilance. If the condition is a form of cancer or precancerous cell, or large enough to press on sensitive structures, specialists here excel in using the technology and depth of experience to make an accurate diagnosis, often down to the genetic level so the best treatment options may be identified. The sophisticated immunohistochemistry tests available at Siteman can characterize individual tumors in ways not before possible and still not possible in many community hospitals.
The determination of benign versus malignant is important. Benign tumors tend to have more defined edges and don’t invade surrounding tissues. When they need to be removed, surgery is the mainstay. Malignant tumors need a more multidisciplinary approach, combining more than one treatment modality. Determining the exact condition, and if cancer, the specific type, often takes more than one approach. Diagnosis is often refined by the pathologist working in conjunction with the surgeon during an operative procedure.
Primary tumors, those originating in the brain or spine, may spread within the central nervous system (brain and spinal cord), but they rarely spread to other parts of the body. For treatment, tumors are classified by the type of cell in which the tumor began, the location of the tumor in the central nervous system, and the grade of the tumor. Tumor grade is a function of how abnormal the tumor looks under a microscope and how quickly the tumor is likely to grow and spread, both very important factors considered in planning your treatment.
Metastatic brain tumors are those that originate in another organ and spread to the brain. Over 90 percent of brain tumors are metastases from other organs. The types of cancer that commonly spread to the brain are cancers of the lung, breast, skin (melanoma), and colon. About half of metastatic spinal cord tumors are caused by lung cancer. The prognosis is better for brain metastases from breast cancer than from other types of primary cancer. The prognosis is worse for brain metastases from colon cancer.
Tests that examine the brain and spinal cord and detect brain and spinal tumors include the following:
CT 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.
MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of the brain and spinal cord. A substance called gadolinium is injected into the patient through a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).
PET scan (positron emission tomography): This imaging looks for 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.
Bone scan: This procedure checks to see 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.
The pathologist determines the grade of the tumor using tissue removed for biopsy. The following grading system may be used for adult brain tumors:
Grade I: The tumor grows slowly, has cells that look similar to normal cells, and rarely spreads into nearby tissues. It may be possible to remove the entire tumor by surgery.
Grade II: The tumor grows slowly, but may spread into nearby tissue and may become a higher-grade tumor.
Grade III: The tumor grows quickly, is likely to spread into nearby tissue, and the tumor cells look very different from normal cells.
Grade IV: The tumor grows very aggressively, has cells that look very different from normal cells, and is difficult to treat successfully.
The chance of recovery (prognosis) and choice of treatment depend on the type, grade, and location of the tumor and whether cancer cells remain after surgery and/or have spread to other parts of the brain.
Genomic Sequencing of the Tumor
With a biopsy a tumor map can be constructed of the tumor, giving important indications of the most promising therapeutic approach and clinical trials. Each cancer is different and may be mixed grades, like some gliomas, adding complexity to treatment.
Specialized pathology studies help in treatment planning by delineating the specific tumor and mutations that predict treatment response. Some masses may look like tumors and, upon analysis of a biopsy, turn out to be plaque from multiple sclerosis, for example. Sometimes a tumor may have a poor prognosis, but a particular mutation it carries improves that prognosis.
Prognosis depends on the following:
- Whether the patient is younger than 60 years.
- Whether there are fewer than 3 tumors in the brain and/or spinal cord.
- The location of the tumors in the brain and/or spinal cord.
- How well the tumor responds to treatment.
- Whether the primary tumor continues to grow or spread