brain tumor
Meaning of brain tumor: Inside a closed skull, even a growth that never spreads anywhere can do harm simply by taking up room.
Definition of brain tumor
A brain tumor is a mass of abnormal cells growing within the brain or in the tissues immediately around it. It may be primary, arising from brain cells or the supporting cells among them, or secondary, formed by cancer cells that traveled to the brain from a tumor elsewhere in the body. Secondary tumors are the more common of the two.
Why does benign not mean harmless here?
Elsewhere in the body a benign growth can push tissue aside and make room. The skull cannot expand, so anything added inside it displaces something else. A slow growing, non-invading tumor can therefore raise the pressure inside the head, block the circulation of the fluid cushioning the brain, provoke seizures, or press on a structure with no spare capacity, such as the nerve to an eye. Location can matter more than malignant potential: a small tumor beside the brain stem is more dangerous than a larger one at the front of the brain, and a tumor wrapped around vital vessels may be impossible to remove completely however slowly it grows. For that reason brain tumors are graded along a scale from slow growing and well defined to rapidly growing and invasive, rather than sorted into two boxes.
How do primary and secondary tumors differ?
| Feature | Primary | Secondary |
|---|---|---|
| Where the cells come from | Brain cells or their supporting cells | A cancer elsewhere, often lung, breast, kidney, bowel or skin |
| What the cells resemble | Nerve or supporting tissue of the brain | The organ of origin, not the brain |
| Number | Usually one | Frequently several at once |
| Spread beyond the nervous system | Rare | Already present by definition |
A metastatic deposit is named for its origin, so cancer that has reached the brain from the lung is treated as lung cancer sitting in the brain.
Why do the symptoms vary so much?
Because function is mapped to place. A tumor in the frontal lobe alters personality, judgment or the strength of one side of the body. In the temporal lobe it disturbs memory and language or sets off seizures. At the back of the brain it takes pieces out of the visual field. In the cerebellum it upsets balance and coordination. Near the pituitary it disrupts hormones and side vision. Separate from all of that is a general set of symptoms caused by rising pressure inside the skull: headache worse on waking or with coughing and straining, nausea, vomiting, drowsiness, and swelling of the optic disc seen when the back of the eye is examined. A first seizure in an adult with no previous seizure disorder is among the more common ways a tumor announces itself.
Used in a sentence
Imaging identified a mass consistent with a brain tumor after the patient presented with new seizures.
Good to know
A metastatic brain tumor, which spreads from cancer elsewhere in the body, is more common than a primary brain tumor originating in brain tissue itself, a distinction that affects both evaluation and treatment planning.
Word origin
Where “brain tumor” comes from
Tumor derives from Latin tumor, meaning swelling, from tumere, to swell, an ordinary Latin word later adopted into medical usage.