It’s natural to be curious about complex medical topics like brain tumors. You wanted to understand how they form, and this guide provides a clear, expert-backed explanation. We will walk through the fundamental biology of cell growth and explore the genetic changes that can lead to the development of a tumor inside the brain.
To understand how a tumor forms, we first need to look at how healthy cells in our body work. Every part of you, including your brain, is made of trillions of cells. These cells have a natural, orderly life cycle. They grow, divide to create new cells when needed, and eventually die when they become old or damaged. This process, called apoptosis, is a form of programmed cell death that keeps our bodies healthy and balanced.
This entire cycle is controlled by a precise set of instructions found in our DNA, which is located inside each cell’s nucleus. Think of DNA as the master blueprint for the cell. Specific parts of this blueprint, called genes, give the orders for everything the cell does, including when to grow, divide, and die.
When this system works correctly, your body only produces the number of cells it needs. For example, if you get a cut, your skin cells divide to create new ones to heal the wound, and then they stop once the job is done.
A brain tumor begins when this orderly process breaks down in a single cell or a small group of cells within the brain. The root cause is almost always a change, or mutation, in the cell’s DNA. This mutation damages the genes that control the cell cycle.
Two critical types of genes are often involved:
When a cell acquires mutations in one or more of these crucial genes, it can begin to ignore the normal signals to stop growing. It starts to divide uncontrollably, creating thousands, then millions, of copies of itself. This growing mass of abnormal cells is what we call a tumor.
It is important to understand that not all tumors found in the brain start there. This leads to a key distinction.
A primary brain tumor is one that originates from the cells within the brain itself or its immediate surroundings. The mutations and uncontrolled growth begin right there. There are over 120 different types of primary brain tumors, named after the type of cell they come from. Some common examples include:
A secondary, or metastatic, brain tumor does not originate in the brain. Instead, it is caused by cancer cells that have spread to the brain from a tumor located in another part of the body, such as the lung, breast, colon, or skin (melanoma). These cells travel through the bloodstream or lymphatic system and begin to grow in the brain. Secondary brain tumors are actually more common than primary brain tumors.
This is the most common question people ask, and unfortunately, the answer is often complex. For the vast majority of primary brain tumors, scientists do not yet know the exact cause of the initial gene mutations. The development of these tumors appears to be a random, spontaneous event inside a cell.
However, researchers have identified a few clear risk factors that can increase a person’s chances of developing a brain tumor.
It is important to note what is not a proven risk factor. Despite popular concern, major scientific and medical organizations like the American Cancer Society and the National Cancer Institute have found no definitive link between cell phone use or head injuries and an increased risk of brain tumors.
What is the difference between a benign and a malignant brain tumor? A benign brain tumor is non-cancerous. Its cells grow slowly and rarely spread to other parts of the brain. However, even a benign tumor can be serious if it grows large and presses on critical areas of the brain. A malignant brain tumor is cancerous. Its cells grow rapidly, invade nearby brain tissue, and can be life-threatening.
Are brain tumors hereditary? Most brain tumors are not hereditary. The vast majority occur in people with no family history of the disease. Only a small fraction, typically less than 10%, are associated with known inherited genetic syndromes that can be passed down in families.
Can lifestyle choices, like diet or exercise, prevent a brain tumor? Currently, there are no known lifestyle changes, diets, or activities that have been scientifically proven to prevent primary brain tumors. Because the exact causes are largely unknown and appear to be related to spontaneous genetic changes, prevention is not currently possible in the same way it is for some other cancers.