“Brain tumors” is a general term that includes both benignant and malignant tumors. They are growths of tissue in various parts of the central nervous system and depending on the genetics and the location of the tumors, they are given several classifications. There are more than one hundred types of brain tumors, and only some of them are malignant. It is important to know about the most common types of brain tumor, and which ones are malignant, mainly because only 33.2% of patients with brain cancer are reported to survive after 5 years in the United States.
In this article, you will be presented with the general terms doctors use to talk about brain tumors, the most common types of brain tumors in general, and the most common among children and adolescents. It is not meant to be a self-diagnose guide but instead a source of helpful information to understand why is there so much variety of brain tumors, and which ones are malignant.
Types and grades of brain tumors
The first thing we need to highlight is that brain tumors is not the same as brain cancer. Tumors can be benign or malignant depending on the alterations found in the cells that make up the cellular growth. So, our first classification of tumors is as follows:
- Benign brain tumors: They often experience slow growth and give out symptoms because they compress nearby structures. They are usually removed, and most of them will not grow back. They have a clear border and do not spread to other areas of the body. Benign brain tumors can be life-threatening depending on the area of the brain they are affecting.
- Malignant brain tumors: They contain cancer cells, which grow rapidly and uncontrollably, invade nearby tissues and may spread to other parts of the nervous system. However, even malignant tumors rarely spread outside the central nervous system. They are a threat to life, and some of them are very difficult to control.
We can also sort brain tumors by grades. The grades of the tumor depend on how abnormal cells look under the microscope. As they become more dangerous, cells would get a higher grade. Thus, we have the following grades:
- Grade I: The cells are very similar to normal brain cells. They have slow growth, and they are considered benign tumors.
- Grade II: There are more alterations in the cells, just enough to say the tissue has become malignant, but they still grow slowly.
- Grade III: The cells look different from healthy tissue, and they are continually growing. It’s a malignant tissue with uncontrolled proliferation (Anaplastic carcinoma)
- Grade IV: The cancerous cells are fast-growing, lose their identity and become entirely different from the original tissue.
Types of brain tumors
There are more than one hundred types of brain tumors, but here is a list of the most common sub-types:
Meningiomas
These are the most common intracranial tumors. There are three different protective layers wrapping the brain and the spinal cord. They are called meninges, and the arachnoid is one of these membranes, resembling a spider web.
Meningiomas are benign growths of arachnoid tissue, and even though they usually have slow growth, they may go unnoticed until they grow big enough to cause alterations. Depending on their location, they would give out several types of signs and symptoms, and some of them might be life-threatening or disabling.
Gliomas
In the brain, there are neurons and additional cells that protect and offer support to neurons, and these are called glial cells. All tumors composed of glial cells are called gliomas, and there are several sub types. They are malignant tumors usually located in the brain, but sometimes in the spinal cord as well. They usually disseminate to other areas of the brain and not to other tissues, and they cause a wide variety of symptoms depending on their location in the brain.
Pituitary Tumors
They are tumors located on the pituitary gland, right in the center of the brain. There are different types of pituitary tumors, and most of them are benign. Since the pituitary is a gland, some pituitary tumors synthesize hormones and cause signs and symptoms, while others may remain silent for a long time unless they grow large enough to press on other structures.
Hemangioblastomas
These are tumors growing from blood vessels, they are very difficult to treat, but luckily enough they grow very slowly and are usually benign. Hemangioblastomas may appear in different areas of the brain, and depending on their location they would give out a series of signs and symptoms.
They are related to a genetic condition called Hippel-Lindau disease, which is a cause of vascular abnormalities throughout the body. When patients have hemangioblastomas caused by this genetic condition, they are likely to get a new tumor after surgery, and when that happens, chemotherapy might be considered as another option.
Acoustic Neuromas
They are also called neurilemmoma and more commonly vestibular schwannomas. Acoustic neuromas are abnormal cellular growths on the vestibulocochlear nerve, the one that connects the ear to the brain. As such, the first symptoms of an acoustic neuroma is a gradual hearing loss and tinnitus, which is the clinical name for a sustained ringing in the ear. They are benign tumors, and they grow very slowly, but as they do, they might cause compression to nearby tissues and other cranial nerves. Thus, they can also cause problems in the facial muscles, facial tingling, headaches, changes in the perception of taste, difficulty swallowing, and confusion.
Brain tumors in children and young adults
Tumors wouldn’t be your first guess when your child is feeling sick. One would think tumors are more common in the elderly, but brain tumors are the exception. They are the most common type of tumor in children, adolescents, and young adults. There is no explanation for most of them, even though some of them might have an inheritance pattern.
In the United Kingdom alone, 400 children are diagnosed with brain tumors every year, and they are usually more common in boys than girls. Not all of them are malignant, but the diagnosis of a brain tumor causes a lot of distress in any parent. That’s why we have prepared a list of brain tumors which are known to be more common in children than adults.
Medulloblastoma
They are by far the most common childhood brain tumors, and they account for up to 20% of brain tumors in children, usually aged 3 to 8 years old, and more common in males than females. It is a tumor of embryonic origin, which start in the earliest of brain cells. It is a malignant tumor that usually spreads through the cerebrospinal fluid to many other areas of the brain and the spinal cord.
Medulloblastoma usually appears near the cerebellum, in an area called posterior fossa. In this area, there is a structure called fourth ventricle, which drains cerebrospinal fluid. When this structure is blocked by the growth of the tumor, it causes a condition called hydrocephalus, which increases the pressure of the cerebrospinal fluid and causes massive headaches. Children may also report feeling too tired, and they have balance problems, nausea, vomiting, blurry vision, and abnormal eye movements.
Pineal Tumors
Up to 8% of childhood brain tumors are located in the pineal gland, a structure located in the center of the brain that releases a series of hormones to the bloodstream. There are many types of pineal tumors, but true pineal cell tumors are those that develop from the pineal gland itself. The most aggressive is called pineoblastoma, and it usually causes a blockade in the normal circulation of cerebrospinal fluid, and several symptoms such as headaches, visual problems, nausea, and vomiting.
Juvenile Pilocytic Astrocytoma
It is another type of brain tumor that occurs more commonly in children than adults. This tumor is not the most common, but it is remarkable because it has a survival rate of 96% after 5 years, which is one of the highest in any brain tumor. This one is not a solid mass but instead a fluid-filled tumor, often called a cyst. It is a benign tumor with a very slow growth, and it does not spread to other areas of the brain.
It usually appears in the cerebellum or the brainstem, and give out symptoms such as headaches, seizures, nausea, and vomiting. Depending on the location they can cause vision problems, hormonal changes, balance and coordination problems, and many other symptoms.
Primitive Neuroectodermal Tumors
These tumors arise from primitive nerve cells in the central nervous system, and they are quite rare. Primitive Neuroectodermal Tumors are more common in children, and they are highly malignant. There are at least three subtypes depending on the tissue of origin, and altogether they account for 4 to 17% of soft tissue tumors in children. In the central nervous system, they cause symptoms depending on their location.
Ependymoma
It is a subtype of glioma that is quite common in children compared to adults. Ependymal cells are a type of glial cell that line the ventricles of the brain, which are fluid-filled structures that drain cerebrospinal fluid. Ependymomas often contain calcifications and cysts. The ependymomas are usually classified in grades depending on how much the tumor cells are different from normal cells.
They account for up to 3% of brain tumors, and 30% of them are diagnosed in children younger than 3 years old. Most of them are located in the posterior fossa, near the cerebellum, and the symptoms they cause are strongly related to their location and how big they grow.
Germ Cell Brain Tumors
Germ cell brain tumors usually grow in the middle of the brain, in an area called suprasellar region, or in the pineal region which is nearby. They are often malignant tumors, but there are many subtypes, such as the teratoma, germinoma, the embryonal carcinoma and the choriocarcinoma, which are more aggressive. They arise from germ cells in the brain, and there are mixed germ cell tumors as well.
They usually spread through the cerebrospinal fluid to other areas in the brain and the central nervous system, and usually start with headaches and vision problems, and hormonal issues if the tumor is located in the suprasellar region. They are not quite common, but they mainly appear in young people under 30 years old.
Craniopharyngiomas
These tumors develop near the hypothalamus and the pituitary gland. It is a benign tumor and undergoes a slow growth, but as it gets bigger, it would start pressing on neighboring structures and cause several signs and symptoms.
These tumors usually appear in children under 10 years old, but they may also affect adults in some cases. The reason why craniopharyngiomas appear is poorly understood, but it is suggested they start forming as the embryo develops during pregnancy, and results from an abnormal transformation of brain cells, which is called metaplasia. This type of tumor is not very frequent, and the symptoms depend on how the tumor grows and the affected brain areas.
Rhabdoid Tumor
This type of childhood tumor is not very common, but it is highly malignant and grows very fast. It is clinically known as atypical teratoid rhabdoid tumor, and it may appear in any given area of the brain or the spinal cord, but most of them start in the brain stem or the cerebellum. It usually appears in children 3 years old and younger, but sometimes it occurs in older patients.
Since this is a very fast-paced tumor, the progression of the symptoms are usually speedy. They may cause symptoms such as nausea and vomiting, headache, coordination and balance problems, asymmetry in the face or in the movements of the eyes, and others. When located near the cerebellum it may impair the normal circulation of cerebrospinal fluid, causing hydrocephalus and increased size of the head.