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Brain cancer

Brain cancer grades

The staging process assesses the spread of cancer beyond the original site. Brain cancer does not behave in the same way as other cancers. Tumors may migrate within the brain, but it is very rare for primary brain tumors to spread outside of the brain, or away from the central nervous system (CNS).

Consequently, brain cancer is usually graded rather than staged. The brain tumor grading system features four distinct grades and provides your care team with an understanding of how the tumor grows. This process helps doctors match brain cancer treatments to individual needs.

Assessing brain tumors

To determine the growth and development of tumors in the brain, doctors focus on the characteristics of the tumor and its effect on functionality. The main factors used to assess brain tumors include:

  • Size and location
  • Type of tissue or cells affected
  • Resectability (the likelihood that part or all of the tumor can be removed by surgery)
  • The spread of the cancer within the brain or spinal cord
  • The possibility the cancer has spread beyond the brain or CNS

A complete assessment will also factor in age and brain cancer symptoms that are limiting basic functions, such as speech, hearing or movement.

Brain cancer grading is much different than staging other cancers in the body. Cancers in the lung, colon and breast are staged based on their location in the body, size, lymph node involvement and possible spread. Tumors in the brain are graded based on how aggressive the tumor cells appear under a microscope.

The grade and resectability of the tumor will help guide treatment decisions. Surgery depends on the tumor’s accessibility (location), size, extent (spread within the brain) and the patient’s overall health (including medical history).

Grade I (grade 1 brain cancer): The tumor grows slowly and rarely spreads into nearby tissues. It may be possible to completely remove the tumor with surgery.

Grade II (grade 2 brain cancer): The tumor grows slowly but may spread into nearby tissues or recur.

Grade III (grade 3 brain cancer): The tumor grows quickly, is likely to spread into nearby tissues, and the tumor cells look very different from normal cells.

Grade IV (grade 4 brain cancer): The tumor grows and spreads very quickly, and the tumor cells do not look like normal cells.

Metastatic brain tumors: Secondary, or metastatic, brain tumors, which have spread to the brain from another location in the body, are much more common than primary brain tumors. These tumors are also becoming increasingly more common as individuals do better with cancer treatment and live longer, giving the original cancer the opportunity to spread to the brain.

Some cancers that commonly spread to the brain are lung, breast, colon, kidney, melanoma, thyroid and uterine. Lung cancer is the most common form of metastatic brain cancer. In fact, lung cancer staging often involves a brain scan.

Metastatic brain cancers will likely be assessed through the Tumor, Node, Metastasized (spread) staging system (TNM). Sometimes, individuals are diagnosed with metastatic brain or spinal cancer before they realize they have another, primary cancer.

Learn more about neurosurgery

Next topic: How is brain cancer diagnosed?