health

Brain tumors vary considerably in their location in the brain, their speed
of growth, whether they are benign or malignant, and the specific symptoms
they produce. Brain tumors can cause damage by direct destruction
of normal brain tissue, by producing inflammation, or by growing so
large that they increase pressure inside the skull and interfere with the
functioning of other parts of the brain. Primary brain tumors can develop
within the brain tissue itself, within the meninges (the membranes that
cover and protect the brain and spinal cord), or within the nerves that
supply the brain and spinal cord.
In adults, the most common types of brain tumors are gliomas and
meningiomas. Gliomas, which account for 78 percent of malignant brain
tumors in adults, arise from glial cells, which are the supportive cells in
brain tissue that nourish nerve cells and hold them in place. Meningiomas
are tumors that arise in the meninges. Ninety percent of mengiomas
are benign; however, these tumors can still cause severe
complications and death because of their location.
The most widely used system for grading brain tumors was introduced
by the World Health Organization (WHO) in 1993. Grading
is based on the tumor’s size, its location in the brain, and how fast
it grows.

• Grade I. These are slow-growing tumors that may not produce
  symptoms for many years. They do not usually spread to other
  parts of the brain and can often be removed completely by
  surgery.
• Grade II. These tumors are also relatively slow-growing. They can,
  however, start to grow more rapidly and may spread into other
• Grade III. Tumors in this category are always malignant and
  spread rapidly into surrounding tissue. Their cells look different
  from those in healthy surrounding tissue.
• Grade IV. These tumors invade other tissues very quickly and are
  difficult to treat. Like Grade III tumors, their cells look very different
  from healthy brain cells.
  parts of the brain.