There are many different brain tumors, but they have one thing in common: There is limited space available in our bony skull, and tumors take up space that healthy brain tissue lacks. This situation is not without problems and can lead to serious, permanent damage.
Forms: What types of brain tumors are there?
Brain tumors are – like all other tumors – uncontrolled cell proliferations of a certain cell type. The brain consists partly of nerve cells (neurons) and partly of a wide variety of cells, such as glial and oligodendroglial cells, which supply the nerve cells with nutrients and surround them with connective tissue.
The brain is protected and cushioned from shock by the bony skull, several meninges, and a fluid called cerebrospinal fluid. This cerebrospinal fluid is produced and filtered in the cerebral ventricles, which are several chambers in the brain. The CSF flows out of these chambers through several orifices and flows around both the brain and the spinal cord.
The cerebral ventricles and brain are made up of different types of cells, and still other cells, the plexus cells, make the CSF. All of these cell types can give rise to tumors, which are named after their tissue of origin: i.e., gliomas, oligodendrogliomas, plexus papillomas. When a tumor is malignant, the tumor cells under the microscope bear little resemblance to the cells from which they originated.
Blastomas and brain metastases
The medical profession expresses this appearance by the name of the tumor: Such tumors are called blastomas, for example, glioblastoma. A common brain tumor in children, medulloblastoma, arises from so-called embryonic tissue, meaning that the cells of origin of the tumor had not yet developed into definitive cell types.
The most common brain tumor of all, meningioma, is not actually a tumor of the brain, but a growth of the soft meninges. However, meningioma is traditionally counted as a brain tumor.
In addition to these tumors, there is the group of brain metastases. Approximately 20 percent of all brain tumors are metastases from other tumors. More than half of all metastases originate from bronchial carcinoma and one third from breast carcinoma. These two tumor types in particular can also lead to generalized spread of tumor cells into the meninges, so-called meningeosis carcinomatosa, which has a particularly unfavorable effect on the course of the disease.
Who is affected by brain tumors?
Brain tumors account for only about two percent of all tumors, but they can occur at all ages and are the most common tumor diseases, especially in children, along with leukemias and lymphatic cancers. A closer look reveals two age peaks, on the one hand the childhood tumors and on the other hand tumors that occur between the ages of 40 and 60.
The tumors differ in their age distribution: while medulloblastoma occurs in childhood, meningioma and glioblastoma are found in patients of older age.
So far, no risk factors have been found that favor the occurrence of a brain tumor; only irradiation of the nervous system (even for therapeutic purposes, for example in the case of leukemia) seems to be a risk factor, especially in childhood. In addition, there are rare hereditary tumor diseases that frequently also develop tumors in the nervous system.
