A brain tumor is a benign or malignant neoplasm which forms and grows in the brain. Classification of brain tumors is done according to the cells that create the tumor. Brain tumors can be also classified as primary and secondary. Primary brain tumors develop inside the brain and originate either from brain tissue or from surrounding membranes. Secondary brain tumors are actually metastases of the primary tumors of some other site.
Primary Brain Tumors
Primary brain tumors can originate from brain cells, brain membranes, cranial nerves, hypophysis, and pineal gland. The cellular mutation is the most common cause of the primary brain tumor. Due to mutations the cells divide rapidly and the tumor grows in time. The mass compresses the surrounding tissue leading to a variety of symptoms and signs. They all depend on the localization of the tumor and its size. The tumors originating from the brain cells are classified according to the cell that forms them and there are acoustic neurinoma, astrocytoma, oligodendroglioma, ependymoma, ependymoblastoma, germ cell tumor, medulloblastoma, meningioma, neuroblastoma and pineoblastoma. Pituitary tumors are mostly adenomas which can be hormonally active or do not have to produce any hormones at all.
Secondary Brain Tumors
Secondary brain tumors are the metastases of tumors of other organs and tissues. There is usually more than one secondary brain tumor or metastasis. In some cases the symptoms and signs caused by the very presence of the secondary tumor in the brain may be the first sign of the primary disease. There are certain types of cancers which are prone to give brain metastases. They include lung cancer (especially small cell lung cancer), breast cancer, colorectal cancer, kidney cancer and melanoma.
So the basic concept is that brain tumors result as a consequence of gene mutation. However, there have not been enough data collected to prove that hypothesis. On the other side there are certain risks of getting a brain tumor.
The Caucasians are more affected by primary brain tumors than other races.
The primary brain tumor occurs more in elderly people. However certain brain tumors are more present in children and young adults. Medulloblastoma is one of them.
Exposure to radiation (ionizing radiation) increases the risk of getting a primary brain tumor. This risk affected all those who have undergone the radiation therapy due to some other primary tumor.
Certain chemicals can be the culprits of primary brain tumor. Chronic exposure increases the risk in comparison to acute exposure.
And finally, if there have been primary brain tumors in a person's family he/ she is at higher risk of developing primary brain tumor as well.