Brain tumors generally fall into two groups, primary brain tumors, and secondary brain tumors. The main difference between the two are where they stem from. Primary brain tumors originate within the brain tissue and may or may not be cancer. Secondary tumors come from cancers or tumors that have spread from another part of the body. These can also be classified as metastatic brain tumors.
1. Primary Brain Tumors
As already mentioned, primary brain tumors are tumors that start within the brain tissue. These can be either cancerous (malignant) or non-cancerous (benign). Since each part of the brain is separated into sections or parts depending on the specific tissue type, these primary brain tumors are named by where in the brain they begin, or the type of brain tissue they started from. The most common of these primary brain tumors are called gliomas. As you can guess, gliomas begin in the glial tissue of the brain, which is considered the brain's supportive tissue. Below are some of the most common types of gliomas:
• Astrocytomas: start from astrocytes, which are small, star-shaped cells, and can occur anywhere in the brain or spinal cord. For adults, this type of brain tumor usually starts in the cerebrum part of the brain. Alternatively, in children, it is more common to see them happen in the brain stem, the cerebrum, and the cerebellum.
• Oligodendrogliomas: start from oligodendites, the cells that produce myelin. Myelin serves as the the fatty covering, protecting nerves. These tumors typically show up in the cerebrum, and grow slowly. As such they do not usually spread to other nearby brain tissue.
• Ependymomas: these can begin in the spinal cord or in the lining of the ventricles. The ventricles of the brain are a set of four interconnected cavities in the brain that are filled with cerebrospinal fluid to cushion the brain. These tumors are most common in children and adolescents, although they could occur at any age.
Other common types of brain tumors don't start in the supportive glial tissue of the brain, but somewhere else. Here are some of the ones we most often see:
• Meningiomas: grow from the meninges, which are the connective tissue layers that cover the brain and spinal cord. These tumors typically grow very slowly and are benign, or non-cancerous growths. They are most commonly seen in middle-aged women, from 30-50 years old. Because for their slow growth, the brain can adjust to accommodate their presence, and it may not be until they are very large tumors that a person starts to have symptoms.
• Schwannomas: are benign tumors that begin from Schwann cells. Schwann cells are the supportive cells of the peripheral nervous system. They produce the myelin sheath that protects the peripheral nerves. These happen mainly in adults and are twice as likely to affect women as men.
• Craniopharyngiomas: These types of brain tumors arise near the hypothalamus, near the pituitary gland. Although typically benign, they can cause issues within the brain and body by pressing on and damaging the hypothalamus. The hypothalamus controls hormone release from the pituitary gland to the body, and therefore affects vital functions like body temperature, hunger, sleep, and fatigue. You see these types of brain tumors mostly in children and adolescents.
• Germ cell tumors: These start from germ cells, or the developing sex cells. These happen when the sex cells that should normally form in the ovaries or testes become trapped in the brain. In essence they never made it to where they were supposed to go. Most of these tumors are malignant, or cancerous.
• Pineal region tumors occur in or around the pineal gland. This gland is a tiny organ at the center of the brain, making it very difficult to reach or removed if need be. These tumors can be either fast, or slow growing with various symptoms indicating there could be a problem.
Secondary Brain Tumors
As mentioned, secondary brain tumors originate from another part of the body, or another cancer which has spread. This means these brain tumors are caused by metastatic cancer. Since this secondary brain tumor has originated from some other cancer, it retains the name of the original cancer. For example, if it began from prostate cancer, it would be considered metastatic prostate cancer to the brain. As such, the cells of the secondary tumors are similar to those from the type of cancer they started.
Treatment for these is all dependent on the original cancer and what treatments it can be responsive to. Similarly, you need to factor in the health of the patient and individualize a plan of care accordingly.