Unlike secondary brain cancer, primary brain cancer rises from the brain tissue itself. This occurs when some of the cervical cells such as astrocytes (also called astroglia) and glial cells (called neuroglia or simply glia) multiply abnormally to form a cancerous mass or malignant tumor. Brain cancer tends to grow rapidly and impacts all vital functions of the brain.
A secondary brain cancer, in the other hand, comes from a cancer of another organ: breast, lung, skin, or cancer of blood cells such as leukemia or lymphoma. In this case, the cancer has spread via the bloodstream or lymphatic system to form metastases in the brain; this condition is called metastatic cancer.
A cancer can develops and remains in one area of the brain. In severe cases, however, the cancer cells may invade many parts of the brain. In this case, the treatment becomes more difficult, and survival chances decrease considerably. Most of the times, even when the cancer is detected, its cause is unknown; however, researchers have identified many risk factors that can lead to brain cancer (see risk factors).