Brain tumors can be divided into two major types: primary brain tumors and secondary brain tumors, also called metastatic brain tumors. Primary brain tumors start in the brain, while secondary brain tumors originate elsewhere in the body. The National Institutes of Health (NIH) adds that "brain tumors are classified depending on the exact site of the tumor, the type of tissue involved, where they are noncancerous (benign) or cancerous (malignant), and other factors." Both types of brain cancers are serious conditions that can affect normal brain function.
Gliomas---Primary Tumors
One of the most common types of primary brain tumors is gliomas, according to the NIH, which form from glial cells---the "supportive" cells in the brain; examples of glial cells are oligodendrocytes, ependymal cells and astrocytes. Three types of gliomas can occur: astrocytic tumors, oligodendroglial tumors and mixed gliomas. Astrocytic tumors start with astrocytes and have three levels of severity: astrocytomas, anaplastic astrocytomas and glioblastomas; glioblastomas are also "the most aggressive type of primary brain tumor," according to the NIH. Oligodendroglial tumors form from oligodendrocytes, while mixed gliomas have a combination of astrocytic and oligodendrocytic beginnings.
Meningiomas---Primary Tumors
The other most common type of primary brain tumor is meningiomas, which the NIH states is a benign brain tumor in 90 percent of the cases. Meningiomas are also more common in women, with the age on onset between ages 40 and 70. The Mayo Clinic states that meningiomas form on the meninges, which are "the membranes that surround [the] brain and spinal cord."
Secondary Tumors
The NIH notes that secondary tumors are more common than primary brain tumors, accounting for 10 to 30 percent of adult cancers. The tumor starts elsewhere in body, where a part of the original tumor breaks off; the NIH lists bladder cancer, lung cancer, kidney cancer, breast cancer and skin cancer as the sources for secondary brain cancers. The separated section of the primary tumor travels through the bloodstream until it reaches the brain, where the secondary tumor forms.
